Without getting more traction, nitrous will only give you more one legged tire smoke. I understood you wanted more dig without adding power. lol
As for working under the car safely, you don't need a lift if you use some good jack stands. The problem occurs if you go under a car being held up by just a jack.

 

about 10 ,depending on how long you run it 30 seconds is average for the road to a minute an size of the tank ,an the track depends on how fast the car goes ,you need to find someone who sells it an remember ,its not the same nos you get at the dentist ,its got a poison in there so it cant be abused ,only for tanks , ,alot of guys use a torch to heat up the bottle ,a heater kit I cheap Dynotunesystems out of mass whole kit 300.00 with the heater ,google it,then iwas told after about 10 times of using it exspect to see smoke comeing from exhaust ,it hard on the top of engine ring pistons,its a blast I did it just before I changed engines ,with 75hp it was noticeable went from like 40 to 70 real fast ,but I desided not to use it on my new engine ,just put the bottle in place ,then I can hook it up later if I choose ,but like said a nitrous kit gets more attention being seen ,then using it ,they sell fake kits too,back 5 years ago I got mine installed for $550.00,takes about 8 hours to install,but the stainless lines are allways there once it done .I would not recommend ,it for more then looks alone ,as its again very hard on the engine,oh they come with a 50hp 75hp 100hp 150hp an 250hp tips an a 3rd selonoid can be had for like $50.00 to add 400hp tip ,its is one of the cheapest ways to get hp ,but the money you may spend later ,you may want a super charger ,not as hard on the engine ,then turbo is getting big to,an I forgot you mention off the line,you want an engine rebuild port an polish heads the super charger ,or turbo ,so I would save ,unless like you you don't mind nitrous just don't use it a lot ,I got to say average people think you have real fast car ,racers they know ,but they may not know how much your running