Extra work during the Notice period because I wanted early release

TL;DR: Resigned for a better career opportunity. Toxic manager is ghosting me, assigning bogus non-SDE work, and won't formally accept my resignation to make me serve the full 2 months. New co. wants me ASAP and is flexible (open to buyout or just resignation acceptance mail). I'm burning out. What's the best way out?

Full Story: My contract has a 2-month notice period. I recently got a much better offer at an AI company and their HR wants me to join ASAP. I explained I could cut my notice period to 1 month since I genuinely don’t have much real work here. I sent my resignation mail asking for an early release, but my manager has been making things hell:

First he discussed once, then started ghosting me (no replies on mail/chat/in person) Gave me random non-SDE work like vendor acquisition, sourcing, market research Made me do overtime without reason When I asked about my resignation being accepted, he just said “i will do it” but never actually did I suspect he’ll deliberately delay everything — maybe won’t even give me a resignation acceptance letter, forget a relieving letter. I asked the new company HR if at least an acceptance mail would work they said yes, but I don’t think I’ll even get that timely. They also said they’re open to a buyout option, but I haven’t raised it with my current employer yet. At this point, the stress is unbearable and I just want to leave ASAP to secure this new opportunity. My questions:

Should I just leave without formal acceptance if the new company is fine with it?

What exactly should I tell the new HR so they’re comfortable without the relieving letter?

Should I try pushing the buyout with my current employer, or is it pointless given my manager’s attitude?

Any advice from people who’ve dealt with toxic managers / long notice periods would really help