Hi there
How are things going now? Same?
Looking at your routine, if he's been refusing the CN a while and is still doping so I would just push those A times to 3hrs. He may well be OT for the push but overall you really ned to reduce the last A time which is far too long before his night sleep. If you push the A time to 3hrs just be prepared to help him with his naps a bit more than usual if he wakes with OT at say 20 mins or so - you can do a W2S and shush/pat him through if this happens. Over a number of days he should get used to the longer A time in the day.
With the night feeds. It's normal for a 6 month old to still have a DF or a NF. It is coming up to the time to drop the NF but not all babies are going to be ready for that at 6 months, if yours isn't ready yet that's fine. I would think one night feed would be enough if he's formula fed although a growth spurt can increase that need but usually only lasts a few days, not weeks.
The 2am feed I would probably make your formula a normal (not watered down) and offer a smaller amount. Then have a separate bottle at the ready with just water. If he drains the smaller amount of milk and is asking for more offer the water.
Taking 3 meals at this age doesn't reduce the need for milk in the night, if anything it can increase it because LO has filled up on solids rather than milk and then still needs the calories from the milk. It sounds like he is only having small solids meals though so I wouldn't worry too much about that. His milk intake during the day should not reduce at all with the introduction of solids - it needs to stay at a good intake for several months yet.
Do make sure you are offering water at solids meal times so that he is not thirsty.
routine might looks like this:
WU 6.30
E 7
E 8 solids
A 3hr
S 9.30 - 11
E 11
E 12 solids
A 3hr
S 2 - 3.30
E 3.30
A 3hr
E 6
BT 6.30
DF/NF 10.30 as much as he wants, formula not watered down
NF 2am ish reduced amount, say the 3oz, water in different bottle if needed (see how this goes as you can likely reduce the oz every couple of days so this feed is gone in a week)
If he is waking early due either OT at night or the first nap coming too early for him then I'd hold out for that nap to come as close to 9.30 as you can. Putting him down earlier may hold off some OT but longer term it can take longer to get your routine back on track. If you watch the clock for a few days and stick as closely as you can to a suitable routine you should, hopefully, help him back on track and get better sleep more quickly.
you might also need to have his meds checked if he has put on weight. I think it might be a couple of months since he started meds now.
I hope this helps