Any legal eagles about to say whether or not he can be extradited to the US to give evidence?
Not as a witness. US subpoenas aren't recognised in UK courts. However they are recognised in US courts (fancy that !) and if one is served correctly on Mr. Windsor, then he would be subject to it immediate upon entering the US.
The problem he will face if he tries to "tough it out" is to then have to worry if he ever lands up anywhere within US jurisdiction. Which could happen by accident, or by "accident" leaving him powerless to refuse.
The most likely example is a changeover flight in the US, since recent changes have removed the protection transit passengers used to have and are now treated (by the US at least) as occurring on US soil. Meaning a diverted flight could suddenly deliver the Prince gift-wrapped to the US authorities. Who will be very pissed off at being ignored.
The FBI could arrange to interview him in the UK. But the optics in the US would really count against that. Don't be fooled by their cutesy apparent obsession with the royals. They fought a long and hard war of independence to throw off the spongers, and are in no mood as a nation to ever be seen to be kowtowing to them ever again.
And whilst it's OK for me to admit I do not possess - nor will ever need - a comprehensively up to date list of every country in the world and it's extradition arrangements with the US, it would not be OK for anyone advising Prince Andrew on such matters. As he could run a very real risk of visiting a country which does honour US subpoenas.