You're very welcome, Meister :D
The screenshake part is entirely up to you, since you know how to do it best, so I'll leave it to you :)
Yes, those weak spots can be attacked with the gun as well, though I found it much easier to hit the second weakspot with the grenades since there's very little space for you to jump up and then shoot at it without touching it by accident :p
Also, I found that the camera was quite tight when following the player's jumping movement, which can be disorienting and would require the full concentration of the player in order to not get dizzy, which would get in the way of making combos read: dashing, jumping and shooting in no particular order, (unless they get used to it), so perhaps you could make the jumping less sudden and the camera could relax it's movements a little?