Because I have autism I am forced to go it alone for writing a
computer science research paper outside of conventional US university
auspices toward a doctorate by publication through an accredited UK or
European university that will offer it.
This is an assumption you've made, and one I'd strongly say is false, off the top of my head I can think of several people with autism in the scientific community that I know, at least a couple of them full professors (and there are probably other's that I know who I'm not thinking of).
As such, I know I must do an unassisted literature search.
Is there some agreed-upon standard between computer science
departments as to how extensive the search must be to meet
professional research standards?
These standards are exactly why people will say you should do a PhD if you want to get into academic research (industry research/R&D is different to academic research). The other reason is that more people who are part of that field means more people you can bounce ideas off or who know key parts of the literature that are relevant to whatever you are working on.
Because of autism I am poor at taking tests and at oral exams. I can't
pass conventional qualifying exams.
If this is the reason you believe you should go it alone and avoid more traditional PhD training, you should change the framing of your question from, "how do I do research alone?" to "which universities can accommodate for my disabilities and how?" Keep in mind a key word you used was conventional. If there is an unconventional way to prove achievement equivalent to what they are testing for that works for you then that solves this problem.
A strong support community, like the kind that develops in a PhD program, is important for producing good results and good papers. If part of the reason you are wanting to "go it alone" so to say is because of social phobias or a preference away from social interaction, keep in mind these people will be the kind who will want to talk to you and go into detail about research while chatting over lunch. Worst case in that scenario, someone might say half jokingly, no work over lunch and half the people will switch to something more conventional while the other half will continue talking about science and just make sure they aren't forcing the dissenting voice to join them.
As a last note, and to confirm your goals, is your goal to get into research and a PhD is a step on this path. Or is it to prove you are skilled/intelligent/smart enough to do research without anyone's help for one reason or another. Despite the fact that basically no one does this, including those who say they did or who everyone else says they did. A PhD is a challenge and involves displaying all of these things even if you get plenty of help and accommodations in order to achieve it.