Summer cross country training?

Hi, I run cross country for Lockport high school in NY and this upcoming season is going to be my last. Last year I ran an 18:40( I think I could of went around a 18:10ish). In track I ran a 4:57 mile and a 11:07 2 mile( again I think I could of gone a bit faster if I learned to push myself better. This year i want to run a 17:00 in cross country. The past couple weeks i've been running around 7 to 8 mile a day at around 7:30 to 8:00 minute mile pace. Around 50 miles a week. And have been doing mile repeats at around 6 minutes after my 7 mile runs. I also just started working out push ups sit ups planks leg lifts etc. I would like for someone to tell me what I should be doing to reach my goal of 17:00 in the xc 5k or any advice and tips are greatly appreciated. Thank you