There's not a list on undone achievements, unfortunately. S'mostly intentional, as a great deal of them are, well, major spoilers.
As for bulwarks, it's mostly just a case of maxing shield wall and tanking your way through the first tier dungeons (which you were doing! Is good.), which'll get you to level twelve or so and open up a fair number of options, including your first unlocked tree, which can bring quite a bit to the table.
Biggest advice in your case (to be considered for your next chara) is to not do kor'pul as your second dungeon. There's six "first tier" dungeons available to all characters (and as many as two more, for some races/classes), and the shade (kor'pul's boss, which is what killed you) is one of the nastier bosses. There's a dungeon to the east of the starting zone (follow the tree line right, until you find a small opening. It'll zig-zag north into a small area with two dungeons and a town.) that has a much easier boss (norgos, in the furthest west/left dungeon in that little area) that you can kill for more experience and a chance at some better loot. Then you can come back and give a try at the shade a bit tougher and better equipped.
As for traps, mostly just pay attention to them -- most of them have set areas of effect and you can avoid them if you're being careful. Remember to rest up after getting damaged (try not to explore unrevealed parts of the map at less than full health, or with talents on cooldown), and don't fight in/on traps if you can avoid it -- and you usually can, though it may mean leading your enemy away from it.
As for what fighter bulwark skills to invest in... best way to help us help you is a character dump or (even better) a link the character's online profile, if you have or can/are willing to make one. Shield wall is a standard thing for fighters, but you can probably safely ignore precise strikes for a while -- it reduces your attack speed, which cuts into your (already hurt from shield wall) damage, and the accuracy isn't terribly needed early on, especially if you're putting some points into dexterity and picking up the passive accuracy booster when you're able. The crit boost is more of a mid/late game thing, when you've got the crit (and a higher dexterity) to really capitalize on it. Early game for a bulwark is mostly tanking it up and beating everything to death with your shield, heh.
Anyway, the biggest habit to break I can think of, that you would have picked up from other roguelikes, is conservation. There are very few limited or unrenewable resources in T4, and unlike many RLs -- RPGs in general -- the melee classes are all very much reliant on regular usage of their active talents. You can (mostly) safely blow everything on every enemy, and then rest up and do it on the next one -- and not only can you, you want to. T4's built such that you're intended to use shield bash (amongst many others) on everything but the most trivial of enemies, so get in the habit of doing that. In DCSS terms, think of yourself as more of a melee-range caster than a fighter or berserker or whathaveyou.