Oh, I'm not offended at all. I'm just glad for feedback. I admit #3 is something I've not heard before. I'll look into it -- I suspect the variables used are involved somehow.
Anyway, unfortunately I have no solution for #1 as of yet. I can't even detect if there is an enemy in front of Giga or behind him. His flinching is only based on the change in his damage percentage, which is why it's so unresponsive to the actual properties of the hit...
As for #2 ... I'm surprised you've been killed at 60-70%! I didn't test very much, to be honest (not enough people to play against). I suppose it could certainly happen though. I know he is severely disadvantaged if at any time he is knocked away after using his double jump -- the only way to stop tumbling then is to attack or Up+B.
There's forced horizontal movement during the whole tumble because otherwise I'd never get him off the stage
Honestly, when I added the ability to DI during tumble it was impossible to kill 'im. I also had to make him unable to act until he travels a far way, because otherwise doing anything would stop his momentum.
Teching, I think that I might be able to add. I'd dread fighting Giga on Shadow Moses, though