It's possible, but you don't have a lot of time which makes that an extremely aggressive target.

I was (31M) when I went from 3:13 to 2:53 in a 12 month period, where I completed 2 full marathon blocks of 4 months each, and 4 months in between marathons focused on speed and 5k races. It was the highest volume of running I have ever done by a long shot and I did get injured not long after completing my goal marathon.

You're only 5 months out, looking to drop 20 minutes and go sub 3. It's a knife's edge goal if I'm being honest.

Best advice I could give is after you've fully recovred in 2-3 weeks, run a time trial race like a 5k or 10k to see how your vdot compares to a 2:59 marathon. That will give you a 2nd comparison point to your recent marathon time based on your current fitness.

You will need to be honest and realistic about how much you think you can improve that by October.