Mon, Weds and Friday sounds fantastic. Later - especially since you are time limited now - you could do more but that should be enough with the other things you are doing to see some big benefits for a while.

Especially if you are time limited I don't think you need to push for an hour.

My favourite session is a running workout known as the Monaghetti Fartleck (named after a famous Australian runner who came up with it)

Warm up - for me about 5 min jog, stretch, 10 mins easy jog and then (without stopping) do the following:

90 sec hard running, 90 sec moderate/easy pace X 2
60 sec hard running, 60 sec moderate/easy pace X 2
45 sec sec hard running, 45 sec moderate/easy pace X 2
30 sec hard running, 30 sec moderate/easy pace X 4
15 sec sec hard running, 15 sec moderate/easy pace X 4

And finish off with an easy jog for 5 or 10 mins and a stretch to warm down.

It's not a time consuming workout but done hard it will make you work. You want to aim to be able to do it without going to too slow in the easy parts and make the shorter hard intervals at least as hard or harder than the longer hard ones. To begin with the most important things is NOT to stop unless you are injured. Then you can learn that however tired you are you can recover on the move to go hard again. Having confidence in my ability to do that has helped me dig deep in a few of my more challenging boxing fights.

I love doing this in a group where the faster people jog back behind everyone else in the easy parts and have to catch up in the hard parts. Gives everyone someone to catch up to or stay in front of and makes it more exciting than when done alone.

Still if you haven't done much running before you might find this is anything but fun when attempting it, especially without company. Many beginner runners find a 30 minute jog challenging enough. There is no shame in that and in that case just doing the time at any pace will build your fitness quickly over the first 2 or 3 weeks.

That workout was one of many which are common in running clubs and often found in running mags. If you want more ideas i can give you a few and you can probably find some on the web. A popular running magazine in Australia is called Runners World and is full of juicy little gems like that one :-)

Some sprinting workouts with rests between sprints will also be valuable closer to boxing competition time. However, moderate length running workouts without stopping are probably best for you right now since you'll burn more fat and set up your running fitness and muscle base in a way which will lower your risk of pulling/straining muscles etc.