A mighty report Lev! Sounds like a perfectly executed race, and a well deserved PB.
My journey to a 2:3x at VLM 2016 started brilliantly today with 1m in 8:56. OK, I was pacing my son on a mile time trial. I thought he did OK for a 7 year old. I might pack in runnng and live vicariously through him.
Luckily my P&D is close to hand. Their schedule has runs Wednesday, Friday and Sunday, all at recovery pace, at 4-6 miles, depending which mileage schedule you were using. But they do also say take whatever time off you need this week.
SS - you live and you learn.! Sounds like a combination of bad luck with the stitch and bad pace judgement. Just put it down to experience, you're a lot faster than 30:10. Good thing about a poor5-miler is you can get back out there and do another ASAP.