On your #3, locktight can be used on any threaded fastener for extra holding power (guys, note that he said 2 electrical and 1 hardware question, so #3 is not an electrical question) but if you're talking about your steering tie rod ends again they need to be machined to make the castle head nuts work. You really don't want to use a nylock or crimp type lock nut in place of the cotter pin. You're risking your life with steering and brake connectors.