You won't get in trouble for sending spam. At worst, you'll just have your account banned on whatever ESP or hosting platform.
Legal action is just something you'll never encounter.
To clean your list, the cheapest way is to send a "blank" message as I call it through something like Interspire Email Marketer (using a VPS through a web host).
Or you can use something like BriteVerify (
http://www.briteverify.com/). It's main benefit is that it doesn't require an Interspire Email Marketer setup. But it's more expensive. Another service would be Verifalia (although I've never used it).
This site here:
https://www.email-validator.net/email-list-validation-cleaning.html is pretty good for verifying emails too. It's pretty much 100% accurate. And you can verify up to 10 emails a day for free. If you want to verify more, just change your IP.
My advice would be to NEVER send to AOL addresses, ever! They'll get you banned on any ESP, because of their high spam complaint rates. Yahoo! addresses are better, but they also have relatively high complaint rates. But I think they're okay to send to.
The toughest ISP to inbox is Gmail, because it's so standoffish. The best ISP of all is Apple, and in this order: @icloud, @me.com and @mac.com
Good luck. I'm still trying to perfect my email marketing method, but right now it's looking bleak because most of the addresses in my list belong to the strictest ISP (Gmail).
And I'm also trying to find the best way to send my emails. If I ever figure it out, I'll tell you how.