Where to start...

Good Afternoon! I am looking for advice from anyone willing to help me out.

Goals:
Modified "run the date" challenge. Unsure what the end results will look like.
Be able to spend a whole day playing paintball (lots of short sprints) without exhaustion
Lose another 40lbs

Current status: 30M 190lbs 5'6" working on getting in better shape (down 30lbs since July with some dieting and exercise) The holidays have killed the progress on the weight loss (I know that's not a real excuse but it is mine for now lol) I know everything will be easier when I get closer to my goal weight and I don't have all the extra weight on my joints.
I have a rower and stationary bike that I had been using essentially every day for the last several months until I ended up with an injury from the primary sport I intend to start playing again next year (bruised ribs along my entire left side). Now that I am healed and feeling better I would like to incorporate running too. I acquired a ~25 year old treadmill that still seems to have plenty of life left in it, obviously it isn't the same as outdoor running, but while the weather is crappy and cold I figured it would be a good starting point. I take walks at work 3 times a day (2x .5 mile and 1x 1.25 mile) so I know I am getting good miles in every month like that.

1. I can pretty comfortably "jog" .5 to .75 of a mile on the treadmill. Would it be better to take the speed back a little and try to go further to increase overall endurance or just push at that jogging pace beyond the comfort limit?

2. What are some recommended running shoes that won't break the bank completely? I have been just using the same under armor sneakers I use for rowing

3. I downloaded the Nike run club app but haven't gotten the chance to try the beginner coaching, is that the best app to at least get myself started or should I look into something else?

4. Any other advice for a newbie that would like to get out and rack up some miles on both his bike and shoes next year?