[@Halvtand]
1. There's no way Piccolo got to 800000 from 3500 in less than two months, when Goku only increased from 8000 to 90000, with a zenkai boost and after training at [i]one hundred times[/i] Earth's normal gravity practically non-stop for six days. That being said, yes, it's totally feasible that Limic's corruption might have affected the fusion in some way, though I feel like it might not need to be the case that Harkon doesn't then improve his power at all after fusing with him. That just seems incongruous to how DBZ itself works; even the weaker characters improve fairly consistently as long as they keep training to improve their power level, after all.
2. Well, of course. All I'm saying is that it's a pretty major thing to need to account for, if a character has a cuts-nearly-everything attack that they can basically spam freely.
3. Oh right, he could do that. Even so, I'd still go with the thing that has a precedent in canon over the thing that doesn't, as a general rule.