What techniques can I use to prevent emails sent from my web site from being marked as spam and increase deliv?

Oh wow. That's going to take a whole book to describe.

Actually let's see about the ones you mention:

1) First of all do not use a proxy server. Especially if it's a free proxy because you're going to be very far from being the only one using that server and somebody else is definitely bound to get the IP of this proxy banned by all servers by doing something very illegal and very bad io if you use that proxy you'll be banned by association.

2) second, you must use some unsubscribe language at the bottom of your email and let anyone who wants to unsubscribe from your newsletter but do not use the standard lingo like: "To unsubscribe click this link". Most spam filters are going to be triggered by that because they know that if this phrase is present in the footer of email it must be coming from one of those services that sends mass email. It can easily block your message just by examining the signature.

You can modify you working I use something like:" your business and your life are in your hands. If you wish to stop getting new knowledge, discounts and other goodies from me please stomp your mouse on this link".

This sounds fun, and is actually pretty unique... Come to think of it, now I will have to change it since it is going to appear everywhere. Just don't be lazy modify it and use something unique.