To actually address the questions in here, the laws in CT are:
- Front windshield: no aftermarket tint
- Front windows: 35% tint cutoff
- Rear side windows and rear windshield (no limit but the a very dark rear window tint can make visibility out of the rear windshield at night very difficult)
I am right at the legal limit on my car with slightly darker on the rear windshield (I think 20%) and can tell you I have never been pulled over for it. If you're driving like an @..hole, it gives cops another reason to pull you over/ticket you, but if you're driving like a normal human, cops probably aren't going to waste their time to pull you over, test the windows, and potential issue you a fix-it ticket.
And on your last point, don't do it yourself. It's not a particularly expensive job and dealing with the film is finicky and would probably cost you more in wasted material/time than the labor cost of a professional installer. Just make sure you're going to a reputable installer that's using good tint (3M has a good reputation). Going cheap on this is how you end up with the tints that start looking purpleish with bubbles forming. I'm 10 years in on mine and looks brand new.