No, he’s simply applying the meaning of the term “gerrymander” to mean voting districts of unequal population, causing inequities in voting representation. He doesn’t mean it literally. He’s not ignorant.
The word he was looking for is “malapportioned”. The Senate is malapportioned (by design). It is not gerrymandered.
The House (in many states) is gerrymandered. It is not malapportioned.
Yes, that’s the correct word. I think he used the word gerrymander for malapportioned to make a point that the Senate has its own problems that are similar to the gerrymandering problem in the House. Anyone who even knows about malapportionment in the Senate probably knows the difference between malapportionment and gerrymandering, I would think, and therefore had a good reason for using the latter instead of the former. But whatever.