Hey Speedyrunner, assuming you're a real person and not just trollin for some replies for grins, good job (if not, great job)! But it's really impossible to tell with the degree of precision that you're asking for whether or not you will run a XX:XX time with the info you've provided.
If we assume your road 5K was an actual 5K (were you able to verify this somehow)? Did you run pretty fast last track season, or is this road 5K kind of a fast anomaly of a race? And, if it was hilly on the second half as you say (and 375ft IS a lot), then you already know you're close without having to ask anyone. XC courses on grass tend to be a little slower than the roads, but Runninglane is known to be fast, so maybe it's a wash in that respect. And, running solo (probably totally solo), at least to me, is a good bit harder to do than if you're in a big race that you're aiming for with a lot of other guys (assuming you're a racer at all that doesn't get in their own way).
Your workouts look fine and good, but again, there isn't a whole lot to be gleaned. I mean, consider how different the 800s would be if your recovery 800s were in 6-6:30 pace instead of a 9-10min shuffle jog? In the first, you'd show a ton of aerobic fitness to run 5:15-25 pace with that kind of speed variation vs just showing that you can run pretty speedily (but not overly so for any sub15 guy). And, your 5:50 pace tempo should really be fairly easy for a guy that can run a min/mile faster for 5K. Same with the long run. Finally, I bet the 16 400s are good (95ft in a quarter, that's nothing to sneeze at!), but what do we know!?
For whatever reason, I want you to make your sub15 goal. That would be very awesome! I know it's tough (esp for a high schooler) to train alone (how does your school not have XC or track!?) and bide your time while everyone else is racing, so great job working through that. There isn't anything that says to me (from what you've provided) that you absolutely can't reach your goal. But, it doesn't matter what me or anyone else thinks, right?! Just keep going, be smart, and then go for it on race day with confidence that you can do it.