Im just an applicant, but I read your post and was in the same exact position last year so thought I would offer my perspective just in case it helps in any way!
I think it is up to what works for you best. Some people do well in cramming in a short period of time... that did not work for me. Where are your gaps? Work on identifying that first. Do you feel confident in the material or do you feel like you will need to do a lot of foundational review before even beginning to practice? Then respectively decide whether you feel more comfortable with a few months of studying or maybe 6 months of studying. It seems as if based on 2, you feel that it is unfavorable to study in your senior year and that it would halt a lot of your activities so I would go with what you feel comfortable with. In regard to #3, for me personally, a longer period of studying actually led to higher yield results because many of my gaps were more foundational and less on the strategy of test taking. The first time I studied, I studied for 3 months in my senior year and bombed the MCAT. The second time, I studied over a 7-month period while in a full-time job during my first gap year and my score increased exponentially (over 12 points). Also, I wouldn't worry about taking too much time off between graduation and applying. In fact, 1-2 gap years is fairly common and can be looked at favorably even.
