[maviczap]

Just replace the brake switch or reattach the spring.

Water in the oil? Has it been sitting around unused for a while. Check the radiator fluid level, is that near the level mark? Change the oil and filter first, doing a head gasket is a big job, and not one of the SV's usual problems. Mayonaise in the oil is usual if its been sat for a while, it'll go after a ride or two.

Popping when running is kinda normal, probably a gap in the exhaust if its had an aftermarket can fitted