Thank you for answering as many of my questions as you feel like!

20PLO Global 5 Handed
MP - 91bb
CO - 131bb
BU (Hero) - 255bb
SB - 100bb
BB - 129bb
_________________

Preflop:
MP - call 1bb
CO - fold
BU (Hero) - raise 4.5bb
SB - call 4bb
BB - call 3.5bb
MP - call 3.5bb

Flop K 4 A(18bb)

SB - check
BB - check
MP - check

Question 1: About what percentage of my range cbets here 4 ways?
-AA, KK, 44
-AK bet, A4 check?
-QJT no flush draw, broadway gutshot + weak flush draw?
-Check everything else seem close?

Hero - bet 14bb
SB - fold
BB - fold
MP - call 14bb

Turn K 4 A 2 (46bb)

MP - bet 34.5bb (38bb behind)

Question 2: Okay now I'm a little stuck.
-I'm going to have a very very small number of 53 hands which I assume are always jamming.
-AA, KK, 44 all jamming?
-AK? A4 with nut flush draw?
-QJT with flush draw?
-Broadway gutshot with nut flush draw?
-Fold everything else?

Question 3: Are there any resources to help me study complicated multiway spots?

I want to crush live 2/5plo games. Multiway pots are complicated and I'm not very good... I've recently started playing a little and studying after years off. I've played poker very seriously at a younger age but now have a career and am just a serious hobbyist. I've been spending lots of time with Matrix and watching some videos (shoutout to Inky, been watching your stream!).

Question 4: Am I asking questions consistent with my goals? I know I've oversimplified the hand categories quite a bit.

Forgive me for not engaging more specifically, but it seems like you have a more overarching MW question, so I'll just give my broader opinion on it:

MW, our bluffs become less effective (just more folks to get off their equity, pretty obvious) and our pot equity decreases as a rule (even towards the top of our range; we're just sharing 100% with more people than we do HU and even the better pieces of the pie get smaller).

As a result, I bet MW flops less frequently and for smaller sizes (while still taking most of my cues from just, like, "common sense poker" and HU flop sims). Even towards the top of my range, I don't want to overinflate the pot because I'm less likely to win it (versus HU). My opponents need a better price to call if I do want to grow the pot at all (as I'm giving up on the vast majority of my air, making my betting range stronger).

Even small bets will thin the field somewhat and (in theory) our opponents will have weaker ranges on the turn, and we can start sizing up again to grow the pot more rapidly and/or apply more pressure against fewer opponents (who will now have significantly less equity/optimism a lot of the time, with only one card to come).