Haha cool =D. Can you use f2 instead of 111 (it's one frame slower). f2 generally does more damage near the beginning of combos cause it doesn't scale much.
Good question. I don't see why f2 wouldn't work but I can't connect it. I think b2d3 has more cancel advantage than the others, so by that logic, there should be a few frames to work with. I am aware that b2d3 has the most hit advantage, but the cancel advantage is also based off recovery frames and b2d3 has only 6 recovery frames and it's +30 so it seems like it has 36 hitstun. 111 and 21 both (seemingly) have 32 hitstun so there is potentially 4 frames to work with depending on the accuracy of that frame data.
I see this potentially being useful to provide an extra (albeit highly gimmicky) mixup. b2d3~df(MB)~dash then either 111 if it hit or b1/b2 if it didn't. Your opponent won't wanna try and poke out cause they're risking the armour absorbing the hit and getting launched anyways.
In terms of damage and going for this regularly, I think it's only really viable for the mixup (if in fact this proves useful). Wasting 2 bars for two extra percent is not worth it.
I think the armor goes away as soon as you dash, and you have to dash in the first few frames of the df(MB) in order to connect 111. If they block b2d3 and you dash cancel, you will be at heavy negative so it's basically a free d1 special for them.
Yeah, it doesn't seem very useful. It might help if you are trying to push your opponent towards an interactable. Like lets say you hit a d2~bola, and you go for j2b2d3 then you dash cancel into 11 bomb plant interactable to reset them. It wouldn't have worked before because you were too far but now you can push them back a little bit more and get that interactable.