Vaccinations and heart worm prevention

[Kasianni]

I am taking the dogs to the vet today for their blood tests (to check for heart worms prior to starting their yearly preventative.) Theo suffers from seizures which I think might have been caused by the Revolution he uses. I don't want to use this product again but want to try something else. This product protects against fleas and ticks and I have never seen a flea in my life nor a tick so does anyone know of a product that is safer then Revolution maybe one that is only for heart worms and other worms. If I see a flea I will treat as we go. I don't want to over load his system. My vet is big on protection and so am I but Theo is not up to par and I am worried. Also, he is due for a rabies shot. Everything I read says not to vaccinate a dog that has seizures. I am really not sure what to do now. He had all his shots as a pup, then the following year but has not had one for 3 years, as you all know they are required every 3 years so he is due. My gut says NO, any advice from anyone that has gone through this? I'd appreciate it. Thanks