So, here is what I came up with. This method doesn't use ANY mods or the horrible "multiplayer hack" exploit (which I really hate), but stays perfectly fine within the rules of the game.
First of all - I set a few goals:
a) "Hammered achievement" as early as possible
b) All quests in Act 1 solved
c) Cat must be saved
d) Alexandar must die twice from death fog
e) Maximizing the outcome from the soul containers in crazy Trompdoys cave (I will create a post about this later)
So, here is how it's done (you need to focus a lot, this is, at times, a bit hard to execute and is REALLY a close call in the beginning):
a) Create a lizard character (must be a lizard, other races won't work here) and give him
* Lone Wolf
* 1 pyrokinetics
* Remainder goes into metamorph (nothing else - SERIOUSLY!!)
* Everything into strength
* Telekinesis
* Very important: Haste skill from pyrokinetics (without this you won't be able to make it)
b) Find weapons - at least there is a knife in the kitchen and a bottle of poison, which you can use to make a poisonous dagger out of it
c) Now go and start a mutiny, kill every magister BEFORE Windego does her nasty thing (it seems to be ok if she does it during the mutiny, I had this on my actual playthrough and still got all the XP) - the other prisoners WILL help you - use the food to buff you and keep regeneration going - DO NOT!! go into the room with Windego before you start the mutiny, but kill every other magister - you can go into the Windego room safely as soon as the mutiny started (or, better, when all the other magisters there are dead)
d) After Windego, kill the dog, then persuade the two magisters in the locked room to stand down, afterwards: kill them (this maximizes XP and is the reason why we need a lizard character: so we get +1 persuasion AND +1 telekinesis at start)
e) Haste, open death fog door - DING!! this is when you will reach level 2 so you can add more points into strength - now QUICKLY fetch the two barrels of death fog which stand next to each other
f) Play as usual - save the other passengers, etc... so when you're already in "damn I waste a lot of potential on my future companion by letting the game ruin their civil ability setup" you go out there as a hero with max XP
g) Now, on the island: put the death fog barrels next to Braccus Rex' statue (lol, how fitting)
h) Let the cat join you, then build - and this is VERY important - a "castle" or "prison" for the cat which she can't leave BEFORE you get anywhere close to Fort Joy (otherwise the cat will be fascinated by that Atusa event)
i) DO NOT start the Atusa event (use the ladder), do your thing, get to level 3 to get the gloves of teleportation, DO NOT leave the fort and DO NOT let get Gawin get away yet (just have him wait at this "secret" entrance before the place where Fane waits
j) Use teleport to throw death fog from above on the "Atusa" group - if you do it right, everyone (except Dallis, for some... reason you will find out about later) dies (yes, you can do this without a fight, but it's a bit tricky)--- et voila: "Hammered" achievement, an amazing hammer weapon, tons of XP and lots, lots of dead magister and Dallis pet scum
k) Now you should be level 4 so you can rob all the good Aerothurge skills from Gawin (the really good skills only appear at vendors when you hit level 4, so I see that all of them survive until this point) before you "help" him with teleport
l) Leave the fort: the cat will be there, alive and well, because you saved her by imprisoning her on the beach (if you don't do this the cat WILL run into the death fog, you can't stop her in any other way)
m) Slay all the magisters and also this brown nosed sourcerer who starts screaming "infidel!!1" at you (forgot his name) - I usually teleport him into the death fog, too - so he can die like the very scumbags he adores

n) Slay the criminals, too (hint: you can flirt with Butter so she will help you against Griff!)
o) Do everything else you want and by the time all the baddies are dead you're well into level 6 and can go for the rest of the island easily
p) ...
q) When you encounter Alexandar again: you will have a second barrel of death fog ;-) just sayin'
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As I said, I will write about Trompdoy later. There is a "trick" you can use to maximize the XP his death gives, which made me giggle when I found out by experimentation this morning.