if you are weak in maths and comp fundamental and you want to compete with MATH, COMP PHD... better to have a second degree and become PHD as well. Master does not really help you, you do not have enough time to pick up the knowledge if you are in a part time master degree.
But please think carefully, you have the talent to do that, don't want you to be regreted. I have studied in MATH department courses in the university, I get a average A in those course but there's still a huge gap between the most talent guy and me. The gap is like when you get more than 60%, you are in a range but always have people get full mark