how do thieves gain skills such as set traps and poison weapon

I have a hacked halfling fighter/assassin on levels 9/11
I don't think it counts, but he has a dexterity of 19 as well
how many traps and poisons should he have per day, and can someone give me a list of which level he gains new ones ? (starting at lvl 1)
eg
lvl 1 - 1 trap, 1 poison
lvl ? - +1 trap and poison
etc

It's based on the kit ability file (Assassin is CLABTH02.2da) in the override folder. Basically it's like this

1 2 3
xxxx yyyy zzzz

which would say gain ability xxxx at level 1, yyyy at level 2 etc.

Most of the abilities are listed as spells and are easily duplicated.

Best way to do this is to use Shadowkeeper. Under the innate tab for the character select kit - you can then add all kit abilities to a certain level. Next level up will continue as normal. (Note however that you also have to remove existing kit abilities or you'll end up with doubled up traps).

If the file isn't there then you can extract it using bifstripper or someone may be able to send you a copy.