Would you say he is an independent sleeper? If he's used to being resettled at night, it would be best to sleep train him rather than helping him resettle all the time so that he learns to resettle himself.. and you would use the pu/pd method to do that.
Do they all share a room? I understand the fear of older children waking up and it might be a rough couple of weeks but things might not get better on their own

If he's teething, you could try some meds before you put him down to help him with the pain.
With regards to A time, the av is anywhere from 3-4 hrs... he's at an age where his sleep will go a little wonky as he's heading towards 1 nap. I've attached a few links for you to look through. If he's waking up crying from his pm nap, it could be an indication of not enough rest... try offering the nap a little earlier (maybe 3.5hrs A from morning nap) to see if that helps and try and resettle if it looks like he needs more sleep.
From 2 to 1 nap transition (10-12m and older)10/ 11mo sleep gone wonky? Read this first! (2-1 switch)If he's only had 2 short naps, I would be tempted to put him down for the night a little earlier too to let him catch up on some sleep.
With regards to feeding, I can't remember exactly how much milk my girls used to have but there is a bottle feeding/feeding solid forum where you could have a look through to get an idea if he's taking enough. I do remember though doing snacks between meals... your dinner is around 4.30pm and I wonder if you could maybe do a light snack around 5.30pm (like yoghurt or something like that) and then a bottle around 6ish before bedtime...