Random thoughts and advice :
-Whatever path you choose, consider one of your primary goals is to stay injury free and progress gradually . You have all summer, don't rush things. It takes time for your body to adapt.
-As some of the others mentioned, slowly introducing to light up-tempo runs will benefit you overall.
-I think you have a shot at hitting your goal, but times on XC courses are not as important as place finishes. Every course is different. Focusing on getting a fit and as you can and staying healthy should be your goal - if you train, eat, and rest, pace yourself properly you will reach your maximum potential.
-Think about jumping into a few local 5K road races between now and XC season. That will give you an opportunity to gauge your progress and not get stale from just training. Don't stress out over them - I idea will be just to keep you sharp and run with some others (with the added benefit of give you some practical speedwork). Even when I am training for 1/2 or full marathons I try and jump in a local 5k every month to six weeks, just to stay sharp.
-The advice about getting some outside coaching is a good one. Almost everyone can benefit for some outside perspective. I was self coached from about 24 up until 38 then finally reached out and got some great coaching from the winner of the 1984 US Olympic marathon trials. Best $$ I ever spent. PR'd in the marathon at close 40 years old.
-Lastly, I was was 18:30 XC in High school (1970s ha!) but was still running 17:00 until I was in my early 40s. (note, I have very limited genetic talent, just stubborn). You can do this, just be smart, be patient, and stay the course.
Keep up posted on your progress!