Deb: I've been a season ticket holder since '93 as well and live in Lowell, so we're coming from roughly the same direction. The only times I've taken the train in all these years are when coming from the opposite direction with someone from Boston, or when I've been alone -- about six times total. Honestly, it's a roll of the dice getting to the game on time and the train is s-l-o-w. I think you're going about it wrong and here is what I do (and what I recommend):
It takes me 70 minutes to get to the parking lot I use leaving home at 9 a.m. (you should hit Route 3 out of Nashua about 8:20). I go down 495, take the Route 1 North exit, and park in the first private lot on the right (office building) immediately after Dunkin' Donuts (you know you're getting close when you see the state police barracks on your right; DD is at the very next intersection). Parking there is $40 and it's a nice place to tailgate. This lot is a little less than 1.5 miles from the stadium, but it's a much shorter walk than it would seem. I head to the stadium at noon and at 12:20 I'm on the concourse with time to hit the restroom, buy a program and grab a drink. Here's the best part of all: after another 15-20 minute walk back to the lot after the game, you can zip into Route 1 southbound traffic IMMEDIATELY without any wait at all. The cars are moving and you're back on 495 northbound pretty fast.
The problem with getting on the train from where you live is you have to travel too far south and east. If you MUST try it, I strongly suggest one of the last stops -- Dedham or the one after (Needham?). You'll have no problem getting seats at either stop. However you choose to go, I'll be interested in how it works out, so drop me a PM if you can.