It seems many onion sites i want to visit gives me a 403 error unable to access with this proxy. Is this the site blocking onion.to or is the site down.

if it is the first is there other proxy options that sites dont block

In Tails you don't need to use proxies like onion.to or tor2web.org to reach hidden services (they're bottlenecks and can MitM you, so using them results in worse performance and security). Just visit the .onion site directly in Tails' iceweasel, e.g. http://jhiwjjlqpyawmpjx.onion for TorMail's hidden service.
Comment by Tails Fri 26 Oct 2012 01:11:59 PM CEST