I know it is easy for me to say try not to worry, and incredibly hard for you to not worry...but do try not to worry xx
The ladies on the breast feeding board are much better fixed to answer your feeding questions. I was unable to BF so my LO was FF from 4 wks old. He could not transition to 4hr E at 4 months and remained on 3hr E until solids were introduced at which time he took *more frequent* feeds as he had his milk then 1hr later solids and right after the solids he demanded a milk top up. I think the milk top up directly after solids only lasted a few weeks but even so it meant something like:
E 7 milk
E 8 breakfast solids
E 8.30 milk top up directly after solids
E 11 milk
E 12 lunch solids
E 12.30 milk top up directly after solids
(nb these times are just example as I am not 100% sure if his E was 3 or 4hrs when he was getting those milk top ups either way though look how often he ate!!!) It felt like I was feeding all day long, I think I probably had a post about it seeming like he ate way too often and was this snacking - turns out this is all totally normal
And now I see heaps of feeding threads I know just how normal it all is.
I've also seen enough threads to know that many mums do a top up just before a nap because of where the E and S sit in the routine and it would end up being too long between E for their baby. I did not do a top up before nap but bare in mind at 5.5 months I was still doing 3hrly E which I had to fit as best I could around nap times.
The thing is, this is just what happens as baby gets bigger. The naps move, the eating moves, they may need a top up, it won't necessarily become snacking and it doesn't need to lead to a feed to sleep prop either. If you think baby is hungry feed him, if once he falls to sleep on the breast after barely a sip this is not a prop, if twice he does this it is not a prop but perhaps a signal that he is not hungry then so you don't need to continue it. I do not think at this age your baby will start snacking, the advice about this is more to do with younger babies who are given a feed at every cry rather than stopping to consider if baby would be hungry, tired or want a cuddle.
WRT your question about the E times above - it is only an example, a guide. You do not need to make baby wait if he is hungry. As a guide I would feed every 4hrs so if he wakes at 40 mins it is unlikely 4hrs have passed since his last feed, maybe wait a little while, if he wakes at 3hrs it will be more like 5hrs between E I would feed right away. In your example then if he wakes at 1hr nap and it has been 4hr or more since E then feed him.
The routine does not need to look strictly like EASEAS, EASAEAS is fine, the point is to have a little bit of A between E and S for most sleeps.
I'm afraid that babies are ever-changing, ever-growing beings which don't come with a manual. Every one is different and every one has their own character, their own ideas about eating and sleeping and their own ideas about how much/long/loud they cry. Routines help immensely, so you know roughly where you are in the day, but don't be ruled by a routine, or ruled by times, remember the routine is there to help you, not to give you more anxiety.
Your baby knows you love him, he knows you are attending to him the best you can, if his food comes a little late or a little early he is not going to suffer dramatically. If his nap comes a bit late or a bit early he is not going to suffer dramatically. You are a caring and attentive parent, please allow yourself to believe this.