1: I'm not sure how much larger class sizes will be, since law schools are somewhat constrained in the short term because of room sizes (especially during COVID) and faculty availability. Schools are undoubtedly hurting for revenues due to losses last year, but I think on average there will be less than 10% more students admitted at selective schools. Lower-tier schools may bring on adjuncts to teach more courses, but I wouldn't recommend going to those schools (especially if they're having core courses taught by non-faculty).
2/3: Yes, many regret going to law school. It is 50% more expensive than an MBA since it's an extra year (though summer internships pay very good money, which defrays this somewhat). My recommendation to law school prospects is to only go if:
(1) you get into a top-3 school
(2) you get a half-ride at a top 20 school, or
(3) you are absolutely dead set on being a lawyer and get into a top-30 school
disclosure: I went to a T14 school on a scholarship, worked in biglaw for 7 years, and now run a startup. I don't regret going to law school. (T14 is the designation for the top 14 law schools, which are relatively fixed in the USNews rankings.)