Try a laser pointer and see if he will chase it. That's an easy way to get a cat to work off some steam. All you have to do is sit in a chair and point around the room. :-) I think a small water bottle your dad can carry around would work well for keeping the cat away from his feet. Or if the cat really likes the laser, just distract him with that.

As for the nails - I'd recommend taking him to the vet. Most clinics will clip their nails for $5-10, and you don't have to worry about him associating any of you with the experience. And of course, keep working on touching his feet so you can do it yourself later.

The Soft Paws are good for some people, but if you can't clip his nails, you aren't going to be able to put those on either. My cats tolerate nail clipping very well, but even they didn't like the Soft Paws application. For one, the nails have to be the right length/thickness or the plastic tips won't fit anyway. Then you have to get the hair out of the way, put in some superglue, try to stick it on and hold it for 5-10 seconds... Didn't work so well for me. Then the cat ended up with bloody toes because she wouldn't quite trying to chew them off.