So many questions....
Your pace in a road race July 4 has little to do with XC. Many people including Geb, maybe the greatest runner ever, don't run well on soft surfaces. If the 6k was in long grass and the 17 min 5k was on packed dirt, same kind of problem.
Same thing with the 5:24 pace. While 5:24 might not be horribly aggressive after running 17 flat, it is still faster. Further, if the first 2k was soft or uphill or if you ran it as a 67 quarter followed by a 5:40 mile then pacing is your problem.
Next, you can't run back to back tempos by mistake if you are anywhere close to burning out. Back to back tempos happen when you are running proper tempo pace and are just feeling so good you can't help it.
Part of your poor race was due to taking Friday completely off. Friday should have been easy, of course, but your body is used to running so 4 or 5 easy miles would have been better.
Another part of your poor race is that you have been working "speed" for 3 weeks. My guess is that you have been running your workouts too fast and you had a 5k race in their as well. Getting used to a different training phase takes about 6 weeks, for 3 or 4 weeks you get slower and only the last 2 weeks will you start to see improvement.
Finally, are you a college freshman? Even if you are not, moving to college is stressful and exciting and so part of your poor race could be attributed to a let down now that you are settling in to college life.
All of this should pass and your 15 weeks of work will pay off. Good luck.