Found more hopeful reading here:
http://www.askthecatdoctor.com/feline-fip.html

Energy: Alert for new objects, but low energy AM/PM
Movement: Mobile, requires effort, made passes at scratching post, slipped out the back door for some backyard grazing, jumped out of cage, wandered the kitchen and living area until settling on bed both AM/PM
Tracking: Slow tracking, did not engage in play. Tracked cat teaser wand. Almond eyes, pupil dilation/contraction, slow response AM/PM.
Appetite: Ate some lifesource bits from dry dog kibble, force fed liquid formula #2
Attitude: Passive, some lethargy.
Hygiene: Fur very unkempt, dry, matted around neck/head area. Observed super-brief self-grooming. Crusty butt*, did #1
Hydration: Sipped from big bowl, took liquid formula

Administered 5mL x2 AM feeding, 8mL x2 PM feeding with formula #2.
Received AM 1mL prednisolone dosage.
AM: jumped out of his cage to hit the dog bed, he was observed to be on top shelf for the majority of the time.
*Exhibited crusty butt (failed cleaning/hygiene, possible diarrhea), but vocally protested baby wipe application, man took care of this.
Directly afterward he then used big litterbox.
Attempted to rinse ruff with water to clean off food spills, fur still matted.
Noticed licking himself around neck afterwards.
Very little vocalization AM/PM.
Continues to exhibit nasal discharge and sounds congested.

Drogo was not disturbed by Hodor coming over to plop down next to him (it’s his bed after all!). Personality seems to indicate he is not stressed or perhaps just oblivious to everything around him.

Formula #1 is quite potent methinks (and very fishy), not to mention that I disliked the vegetable content in the chicken broth. I decided to whip up a new batch of liquid formula (#2) that has more vitamin C to boost Drogo’s viral defense.
3oz raw Pilgrims Pride chicken liver
1 extra large egg yolk
.5oz Simple Truth Organic tomato paste
1 500mg Natures Bounty Vitamin C tablet, crushed to powder (contains vegetable cellulose)
2oz warm water

Blend until liquified.

The question of how much to feed a cat on a liquid diet answered in this article:
https://virtuavet.wordpress.com/2010/03/15/how-to-syringe-feed-a-cat/

The volume a cat can take is 3-6 cc at a time, every 1-2 hours maximum, for a total of about 40-60 cc to fill the stomach at any one sitting.  In a sick cat, it may take 3-6 hours for the food to leave the stomach enough to get a new batch in there!  Good luck!

What a difference zygomatic arch control does for syringe feeding!

Also, based on several reads, warmed food via steam basket and hot water bath, this coupled with the technique in the article led for a successful and quick evening feeding.

I also found a 4-ingredient canned food which looked promising (Applaws Chicken with Pumpkin) but Drogo did not eat.

Did plenty of research on supplementation for sick and FIP-afflicted cats. The general recommendations are (see references):

Vitamin A (liver, kidney, tuna, fish oil, eggs, butter, milk, NOT beta carotene in veggies)
Vitamin C (sodium ascorbate, ascorbic acid, tomato sauce/juice)
Vitamin E (egg yolks, butter are phytate-free sources, avoid greens and seed/nut oils)
Taurine (organ meat, trace amounts in Blue Wilderness large breed adult dry dog food)
Arginine (present in liver and muscle meat, preferably from free range/pasture raised animals)
Omega Fatty Acids: Omega-3 EPA/DHA/GLA (wild caught fish sources)

http://www.angelfire.com/fl/furryboots/fip.html
http://www.dr-addie.com/treatment.htm
http://www.peteducation.com/article.cfm?c=1+1400&aid=665
http://hpathy.com/veterinary-homeopathy/feline-infectious-peritonitis-fip-case-management-and-suggested-new-rubrics-developed-from-500-cases/
http://www.neighborhoodcats.org/how_to_nutrition
http://www.marksdailyapple.com/natural-cat-diet/

Drogo received 5mL liquid formula AM, 10mL total in PM.
Drank water from large bowl due to contaminated dish.
Within 1 hour, used 2 litterboxes.
1mL prednisolone in AM/PM.

CONCERN: New symptom of nasal discharge, wet breathing discovered in PM. At first I was alarmed that he might be displaying labored breathing due to chest effusion, but nose bubbles confirmed that he might have contracted a cold or respiratory infection.

Energy: Alert for new activity, but low energy both AM and PM
Movement: Mobile, requires effort, but will jump down from cage, walk over to bed or cat tree. Made a pass at scratching post.
Tracking: Slow tracking, not really interested. Have not introduced play.
Appetite: Did not observe him eating any hard food, force fed liquid formula
Attitude: Lethargic, appeared tired or subdued
Hygiene:Fur appears unkempt, he did groom himself in an attempt to clean matted hair on his throat, did #1 and #2
Hydration: Sipped from big bowl, took liquid formula

Internet literature suggests that cats prefer warm food to cold, so have to determine a better storage method.

Also feeding too much of the liquid formula induced vomiting in Conan, may have to rethink this formula to include extra Vitamin c.

This was a disheartening day overall as I am not very optimistic with Drogo’s lack of energy and progress.

Found some interesting (hopeful) reading regarding a homeopathic approach to treating FIP.

Went to work today so didn’t have much interaction with kitty. Drogo showed more energy in the morning, even ate twice and used litter box. He showed some interest in ball/string but did not give chase. He has been able to navigate up and down the cage with some effort.

As usual, showed considerable lethargy during evening. Was able to receive full morning and evening 1.5mL dosages of prednisolone. Watched ball/string but did not engage.

Energy: Alert in AM, low in PM
Movement: Mobile, but still has foot drag, requires effort
Tracking: Showed some interest in play, was slow to track string
Appetite: Dog food in AM/PM
Attitude: Lethargic, appeared tired or subdued
Hygiene:Fur appears unkempt, gave him a brushing but seemed a little sensitive, did #1 and #2
Hydration: Sipped a few times today

Drooled a lot when receiving dosages.

Morning IM:
he is back in the game room. he was messing with the ball/string for a minute and now he is kneading the bed
well he brought be the ball/string while i was playing
now he is batting at the string, i have it hanging on your chair
he is vocalizing for attention
he is definitely sharper, he is biting at it and swatting

Energy: Alert in AM, low in PM
Movement: Mobile
Tracking: Showed some interest in play, was slow to track string but was batting at it
Appetite: Dog food in AM/PM
Attitude: Lethargic, appeared tired or feverish?
Hygiene:Fur appears unkempt, gave him a brushing but seemed a little sensitive, did #1 and #2
Hydration: Sipped a few times today

He approached litter boxes in kitchen, but contemplated how to enter
He was more brisk with covering litter this evening
He did go to food bowl in cage around feeding time
He is more vocal today
He is watching ball/string today though didn’t seem to have energy to fetch