One thing I like about your query is that you've obviously not trolling. Sometimes we're not sure. You're just seeking crowdsourced wisdom. That's something that the well-intentioned folks here--those of us who are that--should be able to provide.
I've spent much of my masters years (45-58) in exactly the time-territory you're interested in. PR of 19:28; quite a few sub-20's; now, at 59, happy to break 22.
When I was breaking 20, I was regularly averaging 45 mpw. The key to my training was easy 30 minute jogs 4 days a week: M/Tu/Th/Sat. I discovered as a much younger runner that I couldn't run 6-7 days a week at a moderate pace. Either I ran short/easy, or I ran longer/harder. On my "off" days, I was a jogging fool. Easy/recovery pace these days remains pretty much what it's always been: 9:30-10:15 pace, depending on a range of factors, including the heat, humidity, my weight, intensity of the previous day's workout. On particularly good EZ days, I might get closer to 9:00 pace.
I think that those 7 pounds you mentioned make a big difference. As you lose them, your EZ pace will come down and your other workouts will speed up. Pick up Matt Fitzgerald's RACING WEIGHT for tips on how to lose. Three keys, for me: 1) water; 2) roughage; 3) avoid sugar, pasta, bread, other hi-glycemic carbs.
For a good 5K time, you need a solid aerobic base, tempo runs of 2-3 miles, and some repeat miles, 800s, and 400s.
Two workouts have proved over the years to offer particularly good bang for the buck.
1) tempo intervals, aka Mono fartlek (named after Steve Moneghetti). Instead of a regular 3 mile tempo, run .25 hard, .25 float for the first two and a half miles, then finish with a half mile a little bit slower than the hard pace. Hard pace is 3K; the final half mile is more like 5K pace. That last half mile, after what came before, is a pretty good guide to the 5K pace that you can actually hold. You can run the hard portions faster or slower, depending on how you feel. On the float sections, start by jogging (after the hard segment), then, when your heartrate drops to marathon pace, lock in and accelerate slightly until the next hard stretch.
2) Short steep hill repeats. I do 4-6 and they take exactly 60 seconds. Start with 4 and build up to 6. No need to hammer; if the hill is steep enough, the pain will come. My HR as I drop to a stop twenty yards beyond the crest is about 95% of max. First one easier; then slowly make 'em hurt.
Those two workouts, combined with a regular Sunday 2 hour run (first hour easy; second hour brisk, trending towards tempo if I'm feeling better) get me most of the way to the times you're gunning for.