Hi there, sorry to hear you're having such a tricky time. Hugs.
Looking at your EASY and your situation I'd suggest you go directly to a "stricter" routine to get a suitable, predictable routine established as quickly as possible.
It looks like he is probably UT for those naps. At 5.5 - 6 months an A time of 2hr 30 to 3hrs is the guidance - it is tempting to reduce the A time thinking LO is OT and many parents desperately want to avoid OT but often do not realise that UT is just as hard (if not harder) to deal with.
As it will take a week or two to make the changes and your LO will be 6 months by that time, I would suggest you move to 2hr 30 A time for a few days and then increase to 2hr 45 and then 3hr A time.
For now I would focus on the day sleep, stop feeding to sleep, get the naps in the cot. Use shush/pat or a firm hand to rock in the cot if necessary and ride out the difficult days to get the structure you need implemented.
Your routine would look like:
WU 6
A 2hr 30
S 8.30 - 10 (do not put down earlier than 8.30am)
A 2hr 30 (even after a short nap)
S 12.30 - 2.00
A 2hr 30
CN 4.30 - 5pm
A 2hr
BT 7pm
Then increase A times and focus on establishing the long naps so:
WU 6
A 2hr 45
S 8.45 - 10.15 (use W2S to pat/firm hand/rock through transition to extend nap)
A 2hr 45
S 1 - 2.30 or 3pm
A 2hr 30
CN 5 - 5.15 (shorter CN if naps have been longer)
A 2hr
BT 7.15pm
And then increase to 3hrs, drop the CN
WU 6
A 3hr
S 9 - 10.30
A 3hr
S 1.30 - 3.00
A 3hr
BT 6pm (BT comes earlier due to nap drop)
I would suggest each of those routines for about 3 days - if at some point the routine establishes beautifully before you reach the third routine you can stop where it is working, otherwise plod on with the increase and wait for the routine to establish - it will. Tracy was pretty strict on timings when establishing a routine and although we always adapt routines to fit with LOs needs and take care not to over stimulate or make LO over tired, in these days of routine setting the OS and OT can even help to your advantage so long as you can stick it out.
You will support LO throughout of course, being there when he needs you.
For E times - put them 3-4hrs apart around naps as you have been doing but you will need to stop feeding to sleep if you want LO to become independent. As BT approaches do your E at whatever time it was due after the last nap and do E again before BT even if 3hrs has not passed.
Overnight, for now, I would do what you are currently doing. Nights might change as the day routine changes anyway and tbh I feel you have enough on your plate to cope with. you can look at nights in a couple of weeks perhaps once this day routine is established. Feeding to sleep at night is unlikely to have a huge impact on the ability to self settle in the day, although ultimately you want him to self settle at night too so that you can get a better stretch of sleep.
I hope you find this helpful x
Also, while I am here, if you feel like talking with others or receiving support or even just hugs we have a PPD board here:
Post Partum Depression