Hit submit too soon. 1:35 is definitely too soft. Heck I'd say 1:30 is way too soft. That Saturday workout is no joke, especially given it was hilly. I think you'd be doing yourself a disservice by going out at 1:35 pace, but I'm not sure how much racing experience you have and you don't want to blow up early.
In my goal HM last week, I had been planning a sub 1:27, but knew that was probably a soft goal and I could easily hit it, perhaps getting a 1:25:xx. I surprised myself with 1:23:xx. For various reasons, including some nagging injuries that had finally cleared up, I just didn't have a great gauge on my fitness. Moreover, I'm relatively new to training (so take what I say with a grain of salt) and find that sometimes you sell yourself short when slogging through training on tired legs--the taper and "race day" magic are a remarkable thing. That's why your Saturday workout--done on tired legs, solo, and on hills--is so impressive.
Here's what I did: I tucked in with a group running at a pace I felt was comfortably hard, but sustainable. I didn't look at my watch until Mile 2. When I looked down and saw we were clocking 6'22-6'25, I reassessed my breathing, how I felt, etc. All seemed fine so I stuck with it and dropped the pace in miles 11 and 12, knowing I could afford to pick up the pace at that point in the race.