You're fine. The EMT is considered clinical. I would still do some in-hospital work, at least 200-400 by the time you apply. If the non-clinical work has to be done during summers/breaks, that's fine. Just stick to whatever you do for the next few years. While adComs don't mind the stop/start nature, they don't want to see commitment and consistency. Plus for you, when you're writing your ECs, it helps to build your story.
Finally, don't feel rushed to get this all done so you can apply senior year. I really encourage applicants if they feel they can't commit to school and ECs and do well in both, to take a gap year. For you this can potentially mean a more full-time EMT gig and added volunteering. Applicants always stress about timeline, but it's entirely self-imposed. Do things correctly and at your own pace.