i use a 2x10 to make my first cut and seems like the further i get into a log the slabs come out more and more crooked
View attachment 170554
It sounds like you could have a number of problems. The base problem is if your first cut is not a close to flat as possible, any defects will be magnified in subsequent cuts. Just nailing a 2 x 10 to the log and hoping for the best is asking for problems.
If the bar is diving or lifting during the cut then that could be that the cutters are not filed with the same top plate filing angle. It could also be that your bar is not coplanar with the mill rails, - this happens if the mill is bent, shims under the bar clamps can fix this.
I found I got more consistent straight cuts when I use a solid set of log rails which much better than a single guide board. I use the log rails for every cut and while (like BB) means I can use a Digital angle finder to correct for twist on every cut.
Roughness of cut is the extent to which the cutters dive unevenly into the wood and can be improved by
- making sure the cutters are as even as possible and the chain is not too sloppy in the bar groove - if this is not attended to then the following will magnify any problem
- not see-sawing the CS/mill during the cut, hold the mill at the same angle position all the way thru the wood. When I see lots of see-sawing action I think, blunt chain.
- not pushing too hard, let the saw do as much of cutting as possible.
- pushing evenly, unless you use a winch, few operators can apply a constant forward force. I general use my knees/thighs on the wrap handle, and when I need to take a step forward I pick up the forward pressure using my arms.
- using semi-chisel instead of full chisel.
The images of the cutters are not clear enough to make any judgement. They photos need to be taken as flat to side on as possible. See if you can get one like these.