#1
I have my guitar on the lead channel and:
Gain:8
Treble:8
Bass:4
Mids:5ish

I am in D and when I switch from a power chord from the D to A the A one sounds flimsy, like really weak. When I play around with the settings they both sound very bassy. What do I do?
#2
personally turn down the treble and turn up the mid a tad and that might help but also check ur in tune perfectly and if that doesnt work it could have something to do with your intonation
#4
Let us know if that works - I would say raise the mid.
It might but be a tricky fret - does it sound that way when you play powerchords in E on that guitar?