I currently use wire crates in the car and at home. I do plan on purchasing plastic crates for car travel due to safety concerns (higher possibility of impalement in an accident.)
While driving, I strongly suggest tethering the crate for the same reason, in an accident if the crate is tethered your precious cargo is less likely to be injured.
For quiet time in the crate at home have you tried covering the crate with a blanket? This can help in settling him down by removing some of the stimulation that is going on outside his 'room'
Sounds like you are making some progress, wahoo!
When my pups were little I took them everywhere, car rides, meet and greets at work and with family & friends, errands, etc… I think this is a good thing to do