I was not meaning to offend you, but I have followed T&F pretty close for 30 years or so. I just checked and only 20 guys at the NCAA Division I T&F championships went under a 1:52 last year. That is freekin flying. The 4:20 mile seems pedestrian compared to that, and is a pretty good feat in itself.
I’m pretty sure you wouldn’t even get in the meet if your best time was only 1:52; championship 800s are often tactical so times from that race are not a good indicator. That being said, 1:52 is a very good D1 time.
As to the original poster, you basically need to work on raw speed, from 50m to 400m because that is going to be your limiter. For example 2 x 5 x 300m (48 splits) with 60 seconds rest between reps, 5 minute jog/walk between sets might be a typical miler speed workout for a 4:20 guy; just as a marker go try to do this workout and see what the best pace you can hold is. Your best bet would be to try letsrun, you need real track and field types to give you advice. Realistically to run a 1:52 you need 50.00 400m speed and running 55s should be pretty easy.
Basically, you would probably be doing 1-2 raw speed (400m and less) sessions per week for 4-6 weeks, and then transitioning over to shorter intervals (400-1200m) once you actually start to develop some speed.
Realistically you should think about a 4-5 month training build with racing in months 4 and 5. You are trying to make a huge transition, at a minimum you need to commit to a full season, realistically 2 or 3 seasons if you really want to approach your potential.
You also should seriously consider getting a few coaching sessions to get instruction on speed drills and technique, because developing the mechanics of running fast is very important.