If you want to use XLR, you should buy a matching transformer, but it's not going to have an RCA jack, it will 1/4".
What do I see between the RCA and XLR? Is that a 3.5mm jack? Use that, if it is.
Did you use a Monster cable to send the signal to this sub? It's not uncommon for the end to fit too tightly and pulling the sleeve out is the result. I saw that the first time I used a Monster cable in a car audio system, in the early-'90s. Yanked the sleeve right out of the Alpine power amp and I didn't force it, but it had a death grip on the jack. When they started making guitar cables, Fender saw so many gutted input jacks on new amps that they made a public statement that if a Monster cable was used and the jack was damaged, they wouldn't honor the warranty.