Welcome to the forum. Thanks for your question.
In the question immediately before yours, I wrote a blog-like reply that helps explain why the events you describe carry little or no risk for any STD. Please take a look:
http://www.medhelp.org/posts/STDs/Short-lip-tot-lip-kiss--risk-of-syphilis/show/1861534
Although that discussion emphasizes kissing, the comments also apply to hand-genital contact. Such exposure virtually never carries any risk for any STD. Menstruation or the presence of menstrual blood make no difference; the risk is no higher because of it. To your specific questions:
1) Yes, this was entirely safe.
2,3) The chance any particular female sex worker has HIV is very low, under 1 chance in 1,000. But even if she were infected, there was no risk from this sort of event. In theory, it would elevate the risk if she were recently infected with HIV and in the testing window. But the odds of that are less than one in many million and its not a rational consideration. And even then, this sort of contact would be risk free.
4) The hygiene where you met, or the overall health of the sex worker, make no difference in the STD/HIV risk.
You can assume the sex worker understands the risks. Unless you believe you have an STD, you need not warn her about anything. And for the reasons above, you do not need STD/HIV testing; if you have a regular sex partner, you can safely continue unprotected sex without fear of transmitting anything.
Best wishes-- HHH, MD