So I've got it set to Prefer 5.2 GHz band, and changed the wireless mode to 802.11a only. Everything else I've left the same, still manually set the DNS. It connects like normal, speeds seem to be the same, the only difference is I don't see all the other nearby wireless signals under Networks. I will update on whether it drops or not in the next few hours.
Update: Many thanks Joe Intel, it looks like the wireless card has stabilized. I haven't had any drops in the past ~8 hours or so, so it looks like the problem is fixed. I'll keep monitoring the connection for now.
If you don't mind explaining, I'm curious as to why this solution works? Is there still some sort of incompatibility between the 6205 and Windows 8.1? It seems like the problem is varied and different for each user or computer set up, and different solutions have worked in different cases. Is Intel still working on future drivers for the 6205 to ensure continued compatibility with eventual Windows 8.1 updates? Thanks for your help!