I have some questions about a 2001 Tracker ZR2 I've owned for a while.

1) It makes a buzzing sound during idle or sometimes right after letting off the accelerator when driving or always when backing uphill in reverse. Not sure what would be causing the buzzing sound but it's pretty loud when it happens. Any ideas what it might be or where to start? I thought maybe the transmission but it doesn't seem like anything is wrong there when changing gears.
2) Sometimes when driving the car will jerk or jolt when letting off the accelerator. Any ideas what might cause that?
3) Sometimes the vehicle will kind of cough or hiccup right after starting, or you might think of it as being a little shaky. I was thinking spark plugs but the plugs were replaced just a few years ago. Any ideas?
4) There are small, hard, silver colored droplets on the floor of my garage where I park it but not right under the vehicle so not sure where they would be coming from. Any idea where the vehicle might be dropping a silver liquid substance that would harden? Very weird.
5) Any idea where to find a decent price 4WD actuator pump? My actuator light flashes and I'm pretty sure it's the pump.
6) I need to replace my oil pan gasket but all I have is a hydraulic jack and 4 jack stands. Do you think this is enough to get it high enough off the ground to replace the gasket?

Thanks!