I run to work sometimes. And I run errands sometimes. It's a great way to sneak in some running when you're on a tight schedule. You do have to be well planned out and it sounds like you are. And like LPH said, try to not have anything loose in your pockets, it's super annoying.
I also run splits at times to help get my mileage where I want it. So instead of running 7 miles at once I might do 4 in the AM and 4 again in the PM.
Lastly, I don't think you need to get too hung up on the long run being 40% of your weekly mileage thing. I have done programs successfully and have had coaching clients do the same, where the long run is what it is and the rest of the week my runs are only as much as I need to do to get some hill and speed intervals in. For example, I might have one 5 miler and one 6 miler during the week, but still run 13 to 18 miles on the weekend depending on where I am in my schedule. That's tempered with the fact that I am also cycling.
Living life like there's no tomorrow.
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2007 Look Dura Ace
2010 Custom Tonic cross with discs, SRAM
2012 Moots YBB 2 x 10 Shimano XTR
2014 Soma B-Side SS