OP I have a 5.5 week old DS who has a similar pattern to you. Things I have found helpful are:
Colief in milk- I think this has helped with both silent reflux and colic as it seems his GIT is less ‘spasmy’ with all the gas/milk so less is forced up into the oesophagus.
Bjorn baby bouncer for daytime naps as he’s kept upright so less irritation to the oesopagus causes sensitisation.
As pp suggested- lifting cot up at head end- I’m using books under the feet.
No nighttime nappy changes unless poo.
Keeping baby wrapped snuggly in blanket for night feeds at all times and ending feed as soon as he feeds to sleep (smaller volumes doesn’t seem to affect how long he sleeps for).
White noise- we have an old iPhone with an app on that goes all night. Covers sounds of floor boards and duvet rustling.
They’re not recommended but we use a sleepyhead. I think it’s similarly frowned upon to the cocoonababy (HV and midwife said no to sleep positioners under all circumstances but sleepyhead could be used for supervised naps, we actually use it for nighttime sleep too, we are otherwise low risk for SIDs).
Split shifts like you tried last night- we do this every night or DH does the night so I can sleep.
Bedtime routine of bath or wash, music, lights and massage (tummy and feet seem to be DS’s favourites). DS doesn’t actually go to bed straight after this but spends the evening in the lounge with us. It’s just to get a routine in place at a time when we’d ideally like him to go to bed in the future. We did the same for our DD (now 3) who STTN 7-7 from 4 months and has been a brilliant sleeper since.
Things we haven’t tried yet but are on the list for the future if we need:
Swaddling
Sleeping bag
Sleepyhead on bed so baby feels close
Separate rooms if we are disturbing him
@BelulahBlanca I’d be really interested in seeing the plan you have if it’s possible to PM me? I’m keen to give anything a go! Thanks 