I am an Elf and have tired numerous methods to defeat an upper level boss. I am running out of options so I am asking for help.

I have maxed out my weapon and have filled my inventory with 125 health even though right now I am only at 85. So it fills me to the max each time I use it. The problem I am having is killing a boss with 320 HP and 48 base attack points. If I am lucky and could get to 30 with each attack it would take me 11 attacks minimum which is of course not realistic (not a complaint there). If I add the maximum potential health I have is 85 * 7 which is 595. Granted that would be a perfect. It takes the boss only 11 attacks which seems even the problem lies in the fact that 595 isn't possible but you have restore you health when you are at roughly 50 or then the boss would kill you. Mean that realistically the boss only needs 8 attacks to kill me.

So is there a strategy that I am missing or do I just need to wait until I can get to another couple levels so that my health can increase?

Or is there a way we could purchase a bag or satchel or such that would increase our inventory max? Just an idea.