Hi Jen - those are good times, well done!
This is a nice idea but I'm alot slower than you or Sam - does that matter? Am a 10k-er (current training target to knock 5 mins off my pb early in New Year) who's recently done first half (which I messed up in run-up preparation & insufficient tapering - putting that down to first-time experience so treating it more as a practice run!) with the aim of training up for a marathon possibly the year after next.
I think on increasing your weekly mileage, the general thing is to increase by 10% a week in either distance or time to allow your body to keep up with the training injury-free, with occasional plateau or step-back weeks.
On stride length, the only thing I've come across in my own training so far on this is when a harridan at the gym was trying to get my to increase stride length in speed sessions (have since changed gym!) whereas the advice I got on here was to increase leg speed turnover and the stride length will take care of itself, less risk of injury.
Sam - a handy tool that I use for pacing is on the McMillanRunning.com website where they have a running calculator for endurance, stamina, speed and spring workouts for recovery jogs, long runs, easy runs, steadies, tempos, intervals etc - I use that alot as a rough guideline for pacing runs (just input your current race pace for a distance & it churns it all out for you.)