Studies of efficacy of condoms -- indeed almost any safety device -- generally evaluate what is called "use effectiveness", i.e. the effectiveness in day to day use as reported by people who employ them. Use-effectiveness is what was evaluated in the published studies you cite. This is very different than biological effectiveness, which is similar to how well they work with guaranteed proper use on any single occasion. Anallysis of use effectiveness incorporates imperfections of human behavior:  the studies are based on persons' statements about condom use, recall of proper vs improper use, and so on, i.e. "real world" efficacy. In pregnancy prevention, couples who use condoms as their only form of contraceptions have pretty high rates of pregnancy compared with hormonal contraception, even though the biological efficacy of condoms in preventing conception is nearly 100%. Same deal for HIV and other STDs. The responsible bacteria and viruses cannot transit intact latex or polyurethane; even natural membrane condoms are virtually 100% effective as barriers, despite theoretical concerns about sizes of pores in such membranes. But condoms sometimes break; sometimes are not properly used; and recall of improper vs proper use is imperfect. 

The term "escort" usually implies an expensive female sex worker by appointment, as contrasted with, say, street or brothel workers, bar pick-ups, etc. Such women typically are believed to be at low risk for STDs in general and HIV in particular. They care about their health, select their clients with care (typically men at low risk themselves -- men like you), use condoms, and get tested frequently. In the US and other industrialized countries, probably fewer than 1 in a thousand such women have HIV. With careful condom use, your HIV risk with such partners is far too low, in general, to warrant PEP. If you're in an geographic location where HIV is known to be especially prevalent, or if you experience obvious condom failure, PEP might be warranted, however.

Having said all that, I would strongly recommend that both your and your regular girlfriend -- who presumably may be having her own sexual encounters outside your relationship -- be tested from time to time for HIV and other STDs, especially chlamydia, gonorrhea and syphilis, maybe about once a year. I would do this even if all your extra-regular encounters were condom protected and seemingly safe.

I hope these comments are helpful. Let me know if anything isn't clear.

HHH, MD