Can't connect to FTP or Remote Desktop

I'm a relatively new Xfinity customer and recently discovered that my FTP, remote desktop, SQL Server Management Studio, etc. connections I have for doing web work will just timeout when I try to connect. Web chat support and then a phone supervisor both told me that it's not possible to connect to a private IP using the Xfinity Gateway modem/router with a residential account; my options were either to upgrade to a business plan, or use my own third party modem.

I hooked up a new Netgear Nighthawk CM2000 in place of the Xfinity Gateway with my existing TP-LINK AC-3150 router, but I still get timeouts happening for these connections.

Anyone else experience this? Was I given bad guidance, or is there something else to change on my end?

In a tracert, this is the final successful hop before everything thereafter times out (same result before/after the modem switch):

14    26 ms    30 ms    23 ms  csrkld-gwa01-to70.roc.colospace.net [69.84.222.50]

Any insights/help would be greatly appreciated.

Thanks!