Hi Simmi
Ideally you want to have him in bed at around 7.15ish if he wakes from his last nap at 6.
I would treat that whole awake time as winddown with bath & massage ready for bed. I notice you are cluster feeding at 4,6 and 8, that's fine, I would try the 8o'clock feed at 7/7.15 instead.
As I said we introduced a bedtime routine at around 5 weeks, on the advice of a friend, and it turned out to be the single best piece of advice I was ever given! Our routine then looked something like this:
6pm wake & feed
6.15pm lay ds in cot while you prepare bath and massage stuff etc. I used to give dd one of two things to look at hanging on the side of the cot. (As she got older I started to give her a toy, or perhaps hang an activity centre. Now she has a stuffed lion the same size as her that she wrestles with!). Don't know if ds is sleeping in cot, or moses basket, at the moment. We found this was a great way of getting dd used to her cot each day so when she outgrew her moses and she went in there to sleep there were no transitional problems. 6.35ish bath
6.45is massage if that's what you normally do & get pyjamas on
7ish last feed & into bed.
Bear in mind with any new routine you need to be consistent as it takes will take a while for ds to get used to it. He will realise quickly that bath = bed and it should make your evenings much easier. Once dd got the hang of it she settled like a dream every night. If you find on some evenings he still won't settle, try to stay in his room if poss with the lights way low (if you haven't got a dimmer switch, now is the time to install one!) but if he gets agitated then move to another room but again keep it dim and keep talking and activity to a minimum. He will already be overtired so any extra stimulation will only make him feel worse.
I know sometimes it's hard at the end of the day when you are tired to go through all this but trust me, it's worth it as soon as you get your evenings back to yourselves. Some days it gets to 6pm and I think oh god not bathtime AGAIN I just can't face it, but you know it only takes an hour and then you can relax, and I love that quiet last 15 minutes when dd smells all yummy and has her jammies on and is on my lap having her bottle.
I know you came to the board originally seeking help with naps but perhaps if this helps the evening/ night sleep then his daytime sleep will get more settled too. Give it a go and let us know how you get on. Hang on in there!
kathryn xx