I think you have to have the tests, no matter about work or anything else as you aren't functioning well enough for a "normal" life. Whether you can afford it or not or whether work will end up laying you off and/or you may have to go on disability; those things are in the future but your problems now are here now and need to be sorted out. There is nothing whatsoever to be gained by putting off the medical tests or guessing about what their results might be and whether it all fits together, etc. If the next step is neurological tests, then you need those and the neurologist can interpret the results. The physician's assistant just did preliminary stuff, go get the tests.