It is not easy as an 18 year old without years of solo running experience to disregard the advice of a coach. Were I in his position, with his experience. I'd likely do the same thing, after all the coach with many years of experience probably knows best right?
Crappy coach. I wouldn't run for him, unless you can come to a meeting of the minds about your future training. Discuss mileage goals, appropriate amounts of quality work, when to back off etc...
You can always run unattached. I knew a runner from my club who got cut from his Div I squad, and made it a point to show up to all meets, where his college ran and run unattached. Typically he was beating half or more of the college team.