you can use any switch for a kill switch, looks like all it needs to do is ground that wire there to kill the bike.
the brake thing is pretty simple, it's an on/off setup. Basically you just need to wire that switch in series with the brake light wires
if the winker lights stay on, most likely its the thermal flasher unit. you'll need a new one but make sure it's 6v. also sometimes if the wires get dirty or corroded it doesnt get enough power to trigger the switch to blink.
in all honesty, non of these are problems i'd even worry about at all. I figure as long as the headlight and taillight work and the bike runs good, it's all good to go.