more experienced adwords people may confirm ?, but yes you can place a opt in form, on the premise this form is not the only thing on the page per say or people are required to fill in the form to gain access to the site / or free offer. How ever if the opt is is not part of any option to get access to the site or product such as a short form CPA offer and is more just a grab your newsletter subs then i should be OK.
the redirect is more for conversions than getting around google, so use whatever you know best. Their bots still follow redirect pages, so by making your links redirect is primarily to mask your aff. url from visitors, not to pull one over on google. You can have affiliate links, as long as your page doesnt scream "just click only on this one link, but not these others here or here." Now, im NOT saying make your footer/header links blatent and eye grabbing... just don't try to hide them intentionally. (dont make them too small in font either) Making an actual contact page with a contact form will get you a few brownie points with google. (get one free with google gmail and docs)