We’ve had many of these. We just leaver up the boards and tear them out.

You could plunge cut with a circular saw along the edge. Then work a chisel under it and just tear out the floor boards any way you can.

Then for the screws, I either tear them out with pincer pliers for the shallow ones (you can get decent leverage with pincer pliers). Or just cut them flush with the joists and leave them there (quick work with an angle grinder and cut-off disc).

PS. Sorry been trying to reply to you for a few hours but my client wouldn’t connect.