Dems control the Senate. For the House, would just need a couple repubs to flip. Otherwise it would have to be left vacant I suppose. Mike Johnson being next in line does not worry me.

Correct, Harris would not automatically become the dem nominee. However, assuming Biden’s chosen delegates are loyal to him, I think it’s reasonable to guess they would honor his chosen successor and voluntarily vote according to his wishes.

A convention is a possibility, and I’m not completely against it. It complicates matters severely though, and not for very significant gain since citizens can’t really vote again in such a short timeframe.