You should be proud of your record. However, anyone without a ‘hook’ will have an uphill struggle for a spot at a school as competitive as Williams. The early stats are 30%+ acceptance, but, as mentioned above, that includes athletes and legacies, so the relevant number is below that. Your academics are solid, but will not give you a leg up on your competition. Same for you ECs.
You are right to go early. Your chances in the regular pool will decline substantially. In your application, try to focus on talents or qualities that make you unique. Colleges want to fill classes with individuals with ‘spikes’ - special abilities or personal qualities that set them apart, and that suggest success later in college and beyond. Essentially, you need to find your own hook,
Good luck,