How much has it helped or not? What was your GPU timing before and after and over all latency, before and after as well?
The problem with ndis.sys and dxgkrnl.sys is that those are windows processes and not gpu related--if I am not mistaken. I cannot remember everything associated with those two things off the top of my head. I would need to do some digging, specifically for the gear you have as well. Unfortunately, tweaking the gpu may not do much with those, if anything. (I swear trying to fix these problems is like dealing with a russian nesting doll...)
You could try messing around with different drivers and patches, but as I am sure you are well aware, this is extremely time consuming and can sometimes only produce minimal improvements; at a certain point new gear is the best fix. I will be completely honest, this is something that I usually do by trial and error, step by step, with any computer I try to optimize. I usually keep a chart for each computer I build to keep track of all of this. Some things you can kind of go straight to and tweak expecting there to be a potential roadblock, but other than that, I am still amazed what has to be adjusted on certain computers. (I also hate when there is a problem, you tweak a process to then have to go back and undo this change to find the computer running better than it was before... how does this happen???) This is why I typically prefer to build everything I use, as it helps me trouble shoot down the road. I still have to use a specific Ethernet driver on my main pc and another one on my main slave. It took me forever to find the right ones, but I cannot touch them without causing horrendous issues.
I would say that if you got a reasonable improvement on performance, $50 is pretty nominal for a quality of life improvement. If you feel that it was not worth it, you could return the card if that is still an option, or keep it for a rainy-day.
Sometimes you just need new gear, and with something as mission critical as a master or slave rig, this is an area that I never feel is worth skimping on. At a certain point, it is unavoidable as much as we all despise it.
You could also potentially try getting an SSD for your OS drive and to host your DAW on. I saw that you boot from a mechanical drive. I'm a fan of the tried and true 850evo/pro. The nice thing is if you decide to build a new computer, you could always just pop that SSD over, so it would not be a complete waste of money.
If you keep having issues, is there anyway you could post a pic of the latencymon results or something with your rig setup? Unfortunately, I do not know how much digging I can do at the moment. I am currently in the midst of re-doing my template/studio before a job and trying to fix a thankfully not mission critical computer; I have been procrastinating on the computer for awhile.