It sounds like you are trying to do what we call "going from couch to goal", which can be frustrating. To reach your goal of 1.5 miles in 15 minutes, which is 10 minute mile pace or 2.5 minute quarter mile pace, you need to gradually work into it. Your "plan" would include working up to running further than that distance at a slower pace and also shorter distances faster than that pace, so that both goal pace and goal distance are within your comfort zone.
All that said, I would suggest you start off with 20 to 30 minutes sessions where you run some and walk some. At first it may be mostly walking, but as you progress it will become more running and less walking. Run moderately until you feel winded, although not necessarily "tapped out" then walk until you feel you can run again etc. As you build up endurance you should feel better, run farther and run faster. If you are at 12 minute pace, this becomes a 2.5 mile run.
After a week or so, add in some days where you warm up and then run shorter distances at a faster pace...intervals. Maybe the first time you run 4-6 200's (half a lap) and try to do them in about 1:00 to 1:15 pace each with a minute or two rest between. Eventually work that up to 400's (1 lap) in the same pace shortening the rest if you can. You have then run your 1.5 miles (in 6 pieces) at 8-9 minute pace.
The combination of those two workouts over time should make your goal distance and pace very doable, since you have practiced running both farther and faster.
And since you mentioned weight, each pound of fat is about a mile of capillaries in your body. Any weight you lose reduces the structural load on your bones and muscles and reduces the cardiovascular load on your heart while also making your body more efficient at cooling itself.
Lastly, review videos on "proper running form" and technique so that you are in fact running efficiently. Bad form can wreak havoc.
Hope this helps.