1. What are some alternatives to the pirate bay (for flac/alac music)?
2. What are some free VPNs that allow torrenting?
>as long as i stop seeding as soon as it finishes will i be safe?
No. You'll have uploaded data during the time it was downloading. Also in a lot of jurisdictions the "it's okay if you don't upload" thing doesn't apply and they'll send you letters for downloading.
So yes, you do need a VPN. No, a free one will not do, because if you ain't paying, you're the product. They'll be keeping records of what you do on a free VPN and will cough them up to any lawyer or cop that asks for them. In addition to being congested and slow, due to being free.
Go read this. https://torrentfreak.com/anonymous-vpn-service-provider-review-2015-150228/
I've been torrenting avidly for 12 years on public trackers and never received a letter from my ISP.
Also I really don't like the /g/ widely supporting the never seed mindset. It's true but informing the plebs will only serve to make public trackers even worse.