Hi there
Sorry you didn't have a reply yet.
I'm afraid I can't advise over the teat size but what I can say is that if he is draining the bottles and you are sometimes having to make more then it would be better to make the larger amount for every feed. At the end of any feed the4 bottle should not be drained, there needs to be about an oz left over. If/when they are drained it's a sign to increase the amount you make/offer even if it is not always taken.
During growth spurts the amount needs to increase quite significantly and then after a few days it will reduce back, at those times make sure you offer as much as he wants. After the growth spurt it's probably okay to reduce back down how much you offer but always making sure there is an oz left.
20 - 30 min to take the feed sounds fine.
From memory I am pretty sure you shouldn't re-offer the same bottle when it is 1hr old (ie 1hr from the first offer as this is when saliva hits the bottle) due to possible bacteria growth. Anything you want to offer after that time needs to be a fresh sterilised bottle and fresh formula.
Night feeds continue for a good while yet. At least one is needed until around 8 months or so (this might be a dream feed or a night feed).
During growth spurts you might need more in the night bottle like you do in the day. I don't think there would be any advantage to trying to limit the amount offered because they need those additional calories to grow and they just can't fit it all in during the day, after the growth spurt is over it's usually pretty obvious and the feed goes back to a more normal amount.
do I resist offering a bottle at any other wake ups? What if you think there's a growth spurt in play?
As feeds are usually 3hrs apart (and with just one longer stretch over night) if it has been say 2.5hrs and there is a NW I'd probably try a feed rather than trying to make baby wait another 30 mins. Even during a growth spurt baby is likely to go a reasonable length between feeds, there might be an additional night feed or LO might just need more in the bottle.
If your LO can't quite make it to 3hrs it's okay. Some babies need to be fed on a shorter E time for various reasons. If it's more like 2.5hrs and hard to stretch closer to 3hrs then I'd just go with it until he's a bit bigger.
Sorry I couldn't answer your question about teat size. Hope this is some help.