Not to be impolitic, but if you gained 100 lbs, you are probably outside of the optimal weight range for most stock wheels. They will hold you, but will be more maintenance prone.
Your description reads to me like you have two different goals: go far (tour) and go fast (Ironman). So go into this to address both in the long term.
If it were me, I would:
1. Buy hand built 36 or more spoke wheels. I would go into it with a $5-600 budget, get nice serviceable hubs, double butted spokes, and a touring width rim.
2. Put these wheels on your Specialized with tires that will fit in the frame, and go to town.
3. As the weight comes off, figure out which of your next priorities hit first. Personally, my tastes would run touring first, and the hand built wheels will serve as great touring wheels after the weight is off.
4. If you can, hold off on the "go fast" bike until you are 190 ish. That seems to be the cusp between nice light wheels and Clyde built wheels.
Enjoy your return to the sport, and good luck with the weight loss.