There really isn't anything I can add to the great advice everyone here has already given, including about going clipless.

I just want to add my encouragement that I think when you get set up with clipless pedals, even on this bike, and then a new bike...and then if you do the types of workouts everyone here has recommended...well, I think you are going to improve very rapidly and feel terrific.

If you are riding a heavy steel hybrid, without clipless pedals (and it sounds like without even cages), and you are doing some hilly rides at 12-13mph...I think you are doing great.

Keep at it!! I admire you for doing Tri's...I have not yet had the courage!