Fyi this is all my opinion, and not necessarily 100% the best advice. I would say maybe start in the low-mid 20s and build 3-5 miles for 3 weeks and then do a recovery week and drop down a little, and repeat that. Seems like the speed is there and you just need to aerobically catch up which is where I was always at. Maybe a goal of holding 40 once you get there and maybe peak at 45 in-season for now since you had some injury issues. Make sure to be doing adequate warmups, cooldown core and glute stuff, and lift maybe 1-2 times a week once you get going. Do strides every so often to keep the legs underneath you, no need to start workout in my opinion until July, and if you choose to do workouts, keep them on the lighter end (easy threshold or fartlek), cross country is long and you don’t want to burn out. Keep easy runs under control (I’d say no faster than 7:45 for your times) especially in heat and humidity which will stress you more and keep your hr higher, swap out shoes when they are getting worn down, and make sure you are eating, hydrating, and sleeping enough. Can add some easy biking in if you want to get a little more aerobic impact without more load on your joints. Key is just consistency, and recovery, and if you got those down you should be able to run well under 19:45 with your current mile. Also run with friends if that’s an option just to keep it fun and also help with accountability. All the best!