Samar all of the above can be learned on the job, so focus on maximizing your next opportunity. PM-ing for marketing teams has a ton of overlap with PM-ing for technical teams, so learn how to highlight these similarities for interviews.
You probably won’t be able to find your way into a big-name agency right away, but smaller or mid-sized agency are always looking for managers that are great communicators and detail-oriented. Once in, jump on as many learning opportunities as you can.
(By the way, I would skip the theoretical CS courses unless you think you might become an actual developer. Focus on practical coding resources and reading other people’s code.)