Wow, I'll try to do my best to help you, first, I am no expert but we do have the expert's info at hand here is my favorite interview of Tracy talking about sleeping problems, and she actually addresses problems by age
Sleep – A Q&A Interview with Tracy Hogg
June, 2002
https://babywhispererforums.com/index.php?topic=451.0Also try this book is the best of her books because she talks about specific problems and how to solve them
The Baby Whisperer Solves All Your Problems, (By Teaching you how to ask the right questions)
Now I've read all of the above and I agree with you that the first thing to solve is separating the eating from the feeding, you should try to put him on a routine, EASY routine, and try to keep the routine to at least 3 hours from when you start feeding. Tracy suggests a form of Pu/PD for three months old : "...in addition to the basic procedure..., when you first go in, you may have to reswaddle. Do it while he's laying in the crib. If you can't comfort him in his crib with reassuring words and a soft, reassuring pat, then pick him up. Hold him until he stops crying, but no more than four or five minutes. Don't keep holding him if he's fighting you, arching his back or pushing away from you. Put him down. Again, try to use shush-pat to calm him in the crib. If that doesn't work, pick him up again. On average, PU/PD takes around 20 min to work at three to four months. Luckily even if your baby has developed a habit in response to your accidental parenting, its probably not too entrenched. ...." quote from The Baby Whisperer Solves All Your Problems, (By Teaching you how to ask the right questions) page 228.
So, try doing the routine, when LO wakes up in the morning try to give him a good feed, then A time for 30 to 45 min (depends on how tired you think LO is) and then do a wind down routine (Tracy says for touchy Babies a very calm A time and wind down routine) swaddle him (this really works) and put him to bed, then use the Pu/PD that is detailed above. keep doing it until next feeding time, and also to extend naps. I would address daytime problems first because Tracy says that night time will probably work itself out if daytime is OK.
Try this, again I am no expert, but I really want to help you, Hope it works.
Ana