The WA Dynamic Dropdowns is still supported, it is a part of Data Bridge.
I cant really give much support for a third party dynamic dropdown, To be honest, I Don't even know what i am looking for in the files you provided, I don't know which one works and which doesn't. I don't see how any one of them could work, I don't see any sort of onchange event for any select list on the page you provided.
I am not familiar with the third party script you are using, so really cannot offer a lot of help.