Intense vibrations and spuratic rpms at idle

hello im kinda new to this so some help from someone who really knows what they are talking about would be great.

1.I just recently bought a 2002 svt focus, it runs great pulls hard ect. the only concern i have is that when im at idle the rpms sometimes drop to about 900 and it will stay consistently at 900 then other times it will idle at around 1200, then other times it will idle like im driving a big block with some insane cam and the rpms just keep jumping way down and just catching again.

2.Also, when im idling at a light the car shakes somewhat violently, i notice it mostly in the steering wheel and left mirror, the mirror is useless at the rate that it is vibrating at and the steering wheel gets blury because of the intense vibration.  The car only has 58,000 miles on it and i really dont want to have to be replacing motor mounts already. or if this is just normal in the svt's?

3.yet another issue, at the lot that i bought the car from the battery died. which i beleve the car has some reset safety code that i have to enter to get my radio/clock/cd player working.

4.And another one of my problems is that i believe that it is a cv boot? the rubber accordion looking thing that covers the joint to the wheel. that boot has about a 1 inch tear that has leaked grease.
if anyone who reads this could give me some advice that would be a great help. im a 16 year old kid who is kinda on a budget.
any help out there?