I'm experiencing the exact same thing, including the complete lack of 4G. I remember seeing 4G briefly for a while after I bought the phone in December in another city but assumed when I got home I just didn't have coverage. After several trips to major cities with no 4G I checked with my local store the other day and they confirmed I should have 4G here. They swapped the sim card but that didn't help. They said it was probably a problem with the phone but since I had cracked the screen they wouldn't swap the phone because Verizon would blame any malfunction on misuse based upon the cracked screen. I get it, they can't replace the phone for every idiot that drops their's and cracks the screen. Just sucks that I've realized I've had a problem with my phone for months but since I cracked the screen 2 weeks ago I'm stuck.
I wonder if I would have any luck going the phone route and having a replacement mailed and mailing my phone back or would I just get a bill later? Guess I can try the suggestions here too.