7 weeks isn't long. You'll probably need another week to get over Brighton and throwing in a 2 week taper only leaves you 4 weeks for some decent training. Personally, I'd try and get in another couple of 20+ mile runs and some decent 10-12's midweek. For the 10-12's maybe throw in 30-40 mins at marathon pace. That said I'm not a coach and relatively inexperienced compared to others in here so hopefully you'll get better advice.
Just had a look and for what it's worth my first sub-3 was on the back of a 1.22 HM so you're definitely there or there abouts.
Funnily enough, the marathon I got cramp in was Brighton. Similar to you in my hamstring. It felt like I had been shot in the back of the leg at the time and I looked like an idiot running down the sea front (like a scene from Platoon).
Sorry it didn't go to plan. I went and watched Sunday and there were a lot of painful faces around the 22 mile mark.
Still sub 3:30 is a great time and it gives you something to work on for the next one.