[mch82]

The copyright holder can change the go-forward license at any time. The license doesn’t restrict the copyright holder, it restricts everyone else.

Your employer isn’t seeking a copy of your Apache 2.0 code, which they already have, they’re seeking transfer of copyright ownership.

It really does sound like you’d learn a lot from talking with a lawyer, maybe one recommended by an open source foundation. Lots of lawyers have a first meeting is free policy, so schedule meetings with a few lawyers. Pick the one you like best, or pick none.