First off, I'm curious on why it is unsafe for you to consume more than 12oz of fish in a week. If your concern is about mercury in fish, you may want to research what types are available in your area that have little to no mercury content.
I'm guessing you've already read this thread for information on Protein sources that have worked well for others.
Variety seems to give the best results for most of our members.
Using the pure whey protein 1-2 times a day might work well, especially if you find that you like it in either fruit smoothies or mixed into a coffee drink to conveniently have with other foods. I'm not aware of folks stirring in with vegetables, yet mixing it into oatmeal has worked for some.