You seem to be enjoying what you do, and you're now in your 40s. These are two excellent reasons to make any changes very gradually.
What jumps out at me is your Sunday 15 to 18 mile run at 7 min/mile. That's just 40 seconds per mile slower than your half-marathon race pace, and it's longer. To me, it's crazy for someone like you (or me) to do something like that. Maybe it's defensible for an elite runner who has already maximized everything else and needs to find a way to squeeze out that last .01% of potential, but that's not your situation. I think that run is keeping you from getting what you need out of your other runs. The "tempo" (really "cruise interval" or "critical velocity" or "optimistic 10K paced") workout is also too hard, to my mind, but it's fun to train with other people and that may be worth a slight overreach.
So my advice, from the other side of the 40's, is to do just one long run on the weekends: either 15-18 easy the whole way, or 13 with only the second half gradually progressing to 7 min-pace, if you're feeling good. Maybe alternate those two.
And for two of your four easy days, add 3 x 100m somewhere in the run, and some lunge walking at the end. Your primary objective here is not to get injured. Your secondary objective is gradually to develop a little coordination from the 100s and a little strength from the lunge walks. The 100m repetitions might never get faster than 10K pace, or they might get down to mile race pace or eventually even a bit faster. Don't worry about that. Instead, focus on the feeling of how your body is moving. Pick out some favorite runners to imitate (ideally with opposite styles, like Snell and Ryun; deCastella and Ikangaa; Rudisha and [Clayton] Murphy; etc.). Ease back as soon as you feel any tension. After a few months these might have transformed into 6 x 100 or 4 x 200, but they should never feel like work. If they do, you're doing them wrong. As others have said, let the speed come to you. The lunge walks should start extremely modestly, say right-left-right-left-right-left and you're done--see how sore you feel tomorrow before deciding it was too easy.
So your week might look like this:
M 60min. easy; 40min. easy
T 60 easy; 40 easy plus 3 x 100 relaxed plus a few lunge walks
W Workout with friends (around 90 sec/lap)
Th 60 easy; 40 easy
F 60 easy; 40 easy
Sa 60 easy plus 3 x 100 relaxed plus a few lunge walks
Su Long run: either 15-18 easy the whole way, or 13 gradually progressing to 7 minute pace if you're feeling good.