Is support@pi.uk.com the real blockchain.info's support address? Currently blockchain.info lists that address in the "about us" page, but since the site is behaving erratically, I wonder if it's the real address or a phony one.

I.e. if the site was hacked, the address would likely be replaced with one the attacker has access to, so the info provided on the site itself is not very useful to determine if that address is genuine.
That's the address I used to contact Ben Reeves (blockchain.info's author) a few months ago, so it should be correct. Whether it is still in his control is a different question. He is also known as piuk in the bitcointalk forums.