Ditch all the extra stuff off the BF. Keep only the mudguards.

Get some Rainlegs. These work fairly well. But if the weather is really wet then of course you probably know that everything will get at least damp. A large Ortlieb saddle bag is what is popular with the audax crowd - waterproof with plenty space. For 80mi over two days, I would carry my ultra-light rain jacket, some light weight arm warmers for under the jacket because I dislike the feeling of clammy nylon against the skin, maybe another thin top layer to pull on when it gets unseasonably cold (although I find when riding, the continuous activity is more than enough even in continuous rain to keep me warm). All that stuff except the Rainlegs fits in the jersey pockets along with my road food and I don't even need a big saddle bag.

Another thing: train by riding 60mi or longer rides to increase the size of the legs' fuel tank. That I think is one of the most crucial items, and won't leave you stuffed at the end of day 1.