10 mile walk/jog

Yesterday I drove out to the beach to do a walk/jog workout like the one I did on Tuesday. Honestly, I wasn't sure how far I'd get but if I'm going to walk this race then I've got to get in some walk training. So I started just like before with a 10min walk and a 2 min jog. My first hour went like that. I covered a little over 4 miles and my average pace was 14:19/mi. My leg was doing great and although I didn't want to push it I felt like I could do more. I reset my interval timer for a 10min walk and a 3 min jog. This lasted for about 30min, before I started extending my run time to 4 and 5 minutes. In the end, 2 hours and 20min later, I stopped. I had walk/jogged 10 miles!! The average pace for the last 1hr 20min was 13:47/mi.
I'm relatively happy about all this. At first I had a goal time in mind for this race, now just finishing after all this struggling, would feel great. I'm thinking if I get it to a 10min walk and a 5min run maybe I can get the average pace to 13min/miles. That would make for a 5:40 marathon. Thats long and unimpressive, but I would be stoked!