Welcome to the community.
MrZ, I do understand your desire to limit the technology of destruction. I can’t think of a time that has worked very well in the past. It has been tried here and there through history and opinions vary on how well it has worked.
That said, the biggest problem is that some people will follow the guidelines - the people that don’t tend to be the lawbreakers (by definition) and are also the ones most likely to do harm. The net effect is that you cripple the advancement of the positive benefits without really slowing down the harms. You mention hydrides. I don’t see that as the pacing element for the development of nukes - chemistry is something that any country can develop from scratch without too much trouble. The most common pacing element is the centrifuges. This is the technology to separate and concentrate the correct isotopes of uranium. This is done by making it into a gas form and centrifuge off the heavy molecules that have these atoms. Note that several countries have developed this technology even with international attempts to limit nuclear proliferation.
I can’t address your “letter to the president” question but let me address at the issues you raise.
-Limiting GPU acceleration
There are literally millions of gaming computers that have GPUs in the United States. Every bitcoin site has more than enough GPU power to be considered a super computer. I would say that every engineering workstation has graphics acceleration to run CAD software. My daily driver computer is a ($300 off Amazon) off-lease workstation with a high-end Qudropro GPU in it. This train has left the station.
You are asking this on a site full of hobbyists who code at home. How do you propose to decide who is coding and what is acceptable. Many (most?) of these have computers that are gaming computers that are very powerful. And perfectly capable of running CUDA GPU code.
-Limiting Quantum Computing acceleration
Let me know if you are aware of any running quantum technology. To the best of my knowledge, they are currently working at the single gate level and are far from a working computer.
I would be far more worried about optical computing as a do-able thing.
The question of runaway AI has been the topic of hot discussion for a long time and this is perhaps one of the most thoughtful that I have seen. And it’s free!