You would get a much lower Rds(on) if you used lower Vdss rated MOSFETs. 20v to 60v would be much lower.I am using the high Mosfet because would like to use strong motor of 12VDC.
You can put it on either power supply/return wire to the H-bridge. My personal preference would be to interrupt the positive side.How to connect the Fuse. Is that connect it before the input of 12VDC?
I would not use a P-ch MOSFET. The gate charge is 2.5 times higher in order to get the same Rds(on) for the same Vdss rating as an N-ch power MOSFET.If you have other Mosfet please recommend.