2)AIOs larger than 280mm lack flexibility.
The big ol' 420 fits in the P500A, but only in the front. Over time, you will be forced to get rid of it before it even goes bad, due to noise.
If you still want it, find a chassis that supports such a massive AIO at the top, like the Meshify 2 for example.
4)Memory. Already, the primary timings(18-22-22-42) on that kit are not good, defeating part of the purpose of the 4000mhz kit. https://www.youtube(dot)com/watch?v=AGux0pANft0
Without having to do any manual tuning yourself, you should look towards:
2x 16GB, 3600, 14-15-15-35
2x 16GB, 3600, 16-19-19-39
5)The 4TB storage drive.
Ok, if you're not going to use it for a game library. If you are, it's a little too slow at 5400rpm. Need a 7200rpm spinning drive.
But with the kind of money you're looking to spend, you might as well get a large SATA SSD.
6)No, you don't actually want Noctua IPPC 3000 for this.
I've already gone down that route - put up with using only those - and even their F12 3000 - fans for an entire year.
At the rpm range you'll realistically run them at, you may as well have bought more practical, premium fans, like the normal A14s, or be quiet's Silent Wings 3.