Is it possible to

1-use drum remap on midi?

2-use user audio drums on midi

3-Clear rmx in midi

No one knows?

sorry i never use midi files and rarely use midi styles unless its to convert them into audio styles.

1- no (but you can create user drum and you can use on midifile)
2-yes (use wavesync function)
3-yes (you have to use midisoftware for cleaning sysex data)