Arm DX appears to be priced in comparison to DX at 20 points per level. That is a mistake, however, as Arm DX does not affect Basic Speed and should thus be priced comparably to "just DX" (i.e., DX +1 and Basic Speed -0.25), which is 15 points per level. Otherwise, you'd be better off spending the 15 points to improve your overall DX instead of spending 16 points to only improve your two arms. The easy way to fix this is to make the price comparable to "just DX" at 15 points per level and adjust the value of Arm DX proportionately.

Arm ST has a similar problem in that it appears to be priced in comparison to ST at 10 points per level, while it really should be compared to "just ST" (ST +1 and Hit Points -1) at 8 points per level. The simple solution is to again reduce the values proportionately. Unfortunately, only "Two Arms" can be reduced evenly by 20% (to 4 points), and I'm not willing to have fractional values for a basic advantage. From experience, I can say that the utility of "One Arm" versus "Two Arms" versus "Three Arms" is about the same, really; players will always use their strongest limb(s) unless forced not to. Therefore, I rounded towards the value of "Two Arms", to err on the side of keeping their prices similar.

Regrowth is a different issue. Essentially, it gives you a weaker version of Injury Tolerance (No Eyes [5], No Vitals [5], and Unbreakable Bones [10]) -- you do take the injury, but can grow it back over a long period of time. Considering that for 20 points you can be absolutely immune to dismemberment, it makes no sense to charge 40 points to be able to recover from dismemberment over a long period of time. I think -50% is a conservative value for "Loses the limb/organ but grows it back weeks/months later", which sets a fair value at 10 points.