The only thing I can suggest that might help is some kind of background noise to drown out his car. Like, ocean waves or rain or some shit on YouTube played through speakers in the room where you're looking for peace and quiet.
I had an asshole a couple years back, across the parking lot who would start his no-muffler-having-box-of-shit-car at 4am every morning, let it run for 20-30 minutes (longer in the winter, with an added bonus of a screeching fucking serpentine belt), waking me up two hours early, and leaving me unable to go back to sleep. Day after fucking day. Like you, I approached him, twice, but it didn't matter. Called the cops, didn't matter. Every day, the same shit . The guy was driving me mother. fucking. mad.
I tried different things but, finally, bought a cheap set of 2.1 speakers, set them up inside my bed headboard, connected them to my phone, and played various 10-hour white noise tracks from YouTube while I slept, loud enough to drown him out. It helped. I'd say 90% effective overall. He still woke me now and then, but the white noise at least got me sleeping through most nights.
Eventually, the cunt got a different car, but I still listen to the noise tracks to this day. I've found that I sleep better with them than without them.
I have a pretty good idea of what you're going through, and I sincerely sympathize. But unless you're prepared to go to war with this douchebag, I think the best you can do is drown him out.
Good luck, m8.