Unless your house gets really cold at night, heat mat's are unnecessary. Depending on the size of the viv a 100w bulb will be sufficient at keeping up the temps. This needs to be on a dimming thermostat.

I personally don't like crickets. I always feed locusts - mainly because they have a higher gut loading content than crickets, but crickets are nasty little things, they can nibble on beardies tails and toes should you happen to leave any in the viv and they escape from just about anything.

My Ozzy is not phazed by anything. He used to walk around with my dog. He watches my rats and Guinea Pigs a lot, just out of curiosity more than anything.
My viv has always been on the floor, so he soon got used to animals running by. Maybe if you do this too, he can see the cats walking around but still feel safe in his viv. Of course, don't leave them unsupervised together, but I think they will be fine.