Dan,
The Level 2 plan is designed to get healthy-weight a male, under 40 to a sub 5 hour mark. There are lot’s of variables, but that’s the benchmark.
There really is no other place to go than the Level 3 plan. It’s designed to get that same athlete to a 4:35. But, the Level 3 plan is a beast.
I’d be happy to review your 23 weeks of training and provide feedback on what could be done differently with the Level 2 plan. If you want to take me up on that offer, link your TP account to mine at https://home.trainingpeaks.com/attachtocoach?sharedKey=OKYJVWHNFAPPG and ping me here when you have.
David