Troubleshooting CIO/SLIP with 5M - Lots of Prolonged MOTN Screaming

9 days ago we committed to CIO/SLIP while reading Precious Little Sleep. Our 5M LO previously co-slept and was waking every 1-2 hours to feed and/or fall asleep at the boob. We exclusively feed him breast milk. Also a big cuddler and loves contact naps.

For the first 4 days we saw a decrease in the amount of time it took him to fall asleep (1.5 hours, 45 min, 35 min). Longer than what some people were experiencing but we felt like we were making progress. Night wakings were handled with feedings and then putting him back down. The first couple of nights it worked to delay the first feeding until after midnight. And then night #4 hit: he went down after about 20 minutes of crying then woke at 10:30 PM. Since it wasn't yet midnight, we decided to let him figure out falling back asleep. But he did not fall asleep - he screamed for two hours until 12:30 AM, at which point my wife picked him up to feed him and put him back down. That marked what felt like a regression in the sleep training.

Fast forward: two nights ago he did the same thing, screaming from 5:30-7 AM after feeding at 5 AM, and again last night from 2-5 AM. An important thing to know is that my wife fell asleep in the bed with him from 12-2 AM (by accident) so he fell asleep the old way (boob and cuddle). Before you jump down our throats for letting our baby cry for three hours, we're afraid of picking him up to soothe him a) because it gets in the way of him figuring out how to self-soothe, and b) we're afraid that he'll learn to scream for hours until someone picks him up.

Anomaly to all of this: two nights ago, he fell asleep completely by himself without even a squawk. My wife was out of the house and I bottle fed him 30 min before bed, did our routine, etc. Things were looking good but then he had his 5:30-7 AM scream session and it felt like the bedtime win went straight down the drain.

Multiple-hour scream sessions a week into CIO does not seem normal/expected. We were ready for crying but not to this degree. Are we breaking our baby?

Daytime naps are not figured out. It feels too daunting to try to fix naps when PLS mentions tackling bedtime/night sleep first, and naps second. Any help troubleshooting this would be greatly appreciated. PLS does not appear to be helpful since her troubleshooting is "you're probably doing it wrong." We put our baby to sleep around the same time every night (6:30-7:30 PM, do we need to be more tight on the window?) and we feel he is generally appropriately tired (begins rubbing his eyes, etc). Is our baby too young for this? Do we need to try a different method? Anything else we're not thinking of? It's heartbreaking for us and it's not looking very hopeful for LO right now.

Additional info: no clear WWS, my wife is at home with him while I go to work and she does not really keep track. Bedtime routine is boob/bottle, bath/wipe, diaper, jammies, book(s), prayer (20-30 min). We try to get him up around 7 but some mornings we let him sleep til 8 if he was screaming a lot in the night.