1. 4/5
2. banana >dsmash
Pseudo:
dtilt>dsmash
3. Usually I use this move just for killing, but if I see an opportunity for it that an fsmash probably won't hit then I'll go for it since it's pretty good at damage racking too. Just keep track with if you hit with fsmash or dsmash last and then use the other one for killing. Dsmash is a pretty fast move for a smash attack.
4. Dsmas's 2nd hit (the back hit) is substantially weaker than the first hit so always go for the first hit if you can. Sometimes I'd rather just not hit with the back hit at all since it makes my dsmash staler.
Sometimes against Marths (other characters as well, but mostly Marths) I like to grab them at the edge if I can and then just pummel release them and a good amount of time they'll try to jump up and fair so I dsmash before they can get the fair out and a lot of times it turns into a free gimp since they've already used their midair jump.
