Hi hun and welcome to BW!
First off, let me just say BW is about reading your LO's cues. We would never ever suggest you make a bubba wait if he's hungry before his feeding time. Feeding on demand is fine, except when it becomes a snacking issue like every hour. Many bF babies never manage to get to a 4hr easy until they start solids, so it's perfectly ok to keep to around 3hrs if you feel that's best.
Tracy's ethos was one of trying to out a little A between the E and S so as you don't create a prop for the LO in that they always need to be fed to sleep. That being said, we've all done it, and will continue to do it if our LO is OT or poorly etc, but we try and have a rough easy throughout most days.
2hrs A looks good for a 4mo. Keep this link handy, it's a life saver
Average A times- BOOKMARK ME! Well done you for figuring it out. How does he wake at the 30mims? Does he wake crying or is he happy? I too was plagued with short naps for the longest time, so I'm here to hold your hand and figure it out ok?
Wrt the feeding, just feed when it's due or before if he's hungry. There's a growth spurt at 4mo which always throws a spanner in the works as well as a 4mo sleep regression. If you look through these boards there's thousands that have been where you are now. We've all gotten through it, so I promise, you will too. Sometimes it's just purely developmental and it sorts itself out on it's own, other times we have to tweak a few things. Also, google the wonder weeks.. That also has saved my sanity on more than one occasion.
How does he go down for his naps hun if I may ask? Xx