21 months co-sleeper/breast feeder

[Purlesque]

My Ds went to sleep at 8:30 last night after an hour of feeding and messing about. Between 11:30 and 03:30 he woke up 5 times, it's usually bad but not this bad.
I've been awake since 3:30. This happens at around 4am most mornings, I just can't get back off.

I'm now trying to put in place a proper routine (he has a routine but it shifts every day).
Yesterday I got him up at 7:30 then he napped at 1-2:30, then he fell asleep at 8:30.
Would it be cruel to set an alarm at 7:30 every day? At least until the routine has stuck.
This means he's more likely to nap in the afternoon as he seems to need sleep roughly every 6 hours.

He is really difficult to get into a routine, he just doesn't take to it. So now I'm being more regimented, but itfeels a bit cruel to get him up an 30-60 minutes early.

Excuse mistakes, I'm very sleep deprived.
All this made worse by my own insomnia.

I have an 18month terrible sleeper and no two days are the same, I am wondering if I should do something like this too but then again every day is different for our family as I work shifts, I am not the one to offer advice about sleep related topics but do what suits you i think. It cant hurt to try can it?

just go with the flow.
he's still really young.

with things like this I wonder "to whom does it matter?"
and if the only answer is "me and dh" then decide whether you need him to sleep without your help and if you need him to have a different routine. with dd I've learned that the routine she sets is fine and I can largely fit round her.