These seem like two separate issues.
For the first, roll back to the previous driver version and see if your black screens on the 2K monitor go away. I'm still rocking 24.5.1 on my 7900 XT and working great.
To address the second, list your full system specs. Sounds like your cooling system may not be enough for a six hour gaming session.
Ryzen R7 5700X | B550 Gaming X | 2x16GB G.Skill 3600 | Radeon RX 7900XT
Ryzen R7 5700G | B550 Gaming X | 2x8GB G.Skill 4000 | Radeon Vega 8 IGP
Ryzen R5 5600 | B550 Gaming Edge | 4x8GB G.Skill 3600 | Radeon RX 6800XT