Don't let anyone put you off doing the right thing. You are great, if only there were more kind hearted people like you around how much better it would be for the animals of the world.
My kitten Scooter was a rescued semi feral we found crying pitifully under a piece of corrugated iron...
Some cats just hate car travel and apart from sedating them I don't think there is much you can do about it.
Our cat Felix poops, pees vomits and screams like a banshee all the way to the vet/boarding kennel. We have tried everything we can think of and have not found anything that will work...