You talk about the amps adjustment on your foot pedal being too sensetive...have you tried turning the main amperage dial on the machine down? say if you turn the main amperage to 300 amps. then the amps can be varied from 0-300 amps. this would be considered too sensetive for most welders. but, say if you turn the main amperage dial to 50 amps, now the foot pedal varies the amps from 0-50 amps and gives you a lot more control over the heat. try that out and see how you like it. if what you're welding needs more heat turn up the main amps control until all you have to do is push the pedal all the way down and you have the optimum heat...no guesswork.
and yes, there are add-ons you can get for your TIG torch so you can vary the amps w/ your thumb or fingers. check out www.lincolnelectric.com or www.millerwelds.com. they're fairly popular, so you shouldn't have any problems finding one.