You have given me a LOT to cover so here it goes!
Likely overkill, better to have and not need right!
I am not reading all the specs - just watch how your dual M.2 slots work and if they disable SATA ports when both in use, which ones and if you need those SATA ports. Usually in the manual, not the web specs.
Depending on the board, it will only run at most 2933mhz without overclocking to XMP. I don’t run XMP (tried with little change) but that’s room to push as it ages.
240 would be the smallest I would do!
Personally, I never trust a single drive and like have separate I/O for Windows but NVME I think can handle it. All drives are still bad at mass number of small files being used at once though still. Good thing our textures and terrain are MASSIVE.
It won’t register, your license key is tied to the motherboard. Install again anyway and call your MS Activations hotline and they will re-assign it for you no charge. I have posted on doing so before, but the North American number may be of no use to you!
Edit 2: Windows Key
If you can access the old Windows drive once rebuilt, you can extract your key and reactivate that way (or if you have a sticker then you are OK - mine was a free Win7 upgrade that attaches to your MS account so I don’t have a key per se).
Edit 1: Forgot the CPU!
Looks good to me, I am just always weary of the KF’s for one reason not related to them directly. Anyway, a KF is a K with a defective & disabled onboard GPU. So you get some extra thermal headroom for CPU overclocks. However, if your graphics card calls quits - you’re out of the fight until you get a new one. I like having the onboard GPU as a backup since a few of my GPUs were replaced through death, not just age. If that PC is solely gaming and you have other means to access documents/internet etc, then no worries.