It actually isn't an exaggerated comparison at all. My Dell Precision M6700 laptop would outperform your server head to head. My M6700 has the i7-3940XM, 32GB RAM and 1.25TB of SSD storage and scores over 16000 for a GeekBench benchmark, where a AMD 6212 system scores in the 12000 range.

This was exactly what the recommendation was geared at, you've just taken it as a personal attack. Above you admit that you aren't an expert here and some decisions may not have been the right ones. Bringing an industry expert in can help you understand the what and why and can be the fastest way to solve your problem while also obtaining knowledge transfer. I used to bring consultants in as a DBA all the time because no one can be an expert in everything and having the right resource available prevents problems from occurring. If you are dedicated to doing it on your own, you have to expect that at some points people are going to point out mistakes you are making or have made, and that you might hit a limit to what information is practical to put into a forum thread. I used to write multi-page explanations of SQL Server internals on forum threads, I won't do that anymore because it requires to much time.

The configuration you are trying to obtain doesn't make sense. With 4 NUMA nodes and 4 instances I would just use ALTER SERVER CONFIGURATION and set the process affinity for each instance to a specific node. The theory behind reserving CPU 0 and 15 for the OS is good in theory, but not in the reality of how OS scheduling occurs or other process scheduling is going to occur. In all my time working with SQL Server I've only once had to reserve CPUs for the OS and it was for a separate application that was running on the server and it had it's own process affinity settings to make it run on those CPUs. You are over complicating things here for no real net gain other than you promised something that I wouldn't have recommended promising.