SMB is blocked by 90% of ISP's around the world.. the number of unprotected windows computers that would be exposed opening SMB would probably cause the WWW to collapse.
SMB is entirely unsafe.. it is a local LAN protocol to never ever be used over the internet. It has poor security and when people setup LAN sharing it is often setup with none.
The TC does not expose SMB to WAN.. only AFP..
And no windows computer has AFP protocol add ons.
Summary.. it cannot be done.
Now the right way.. Use a Mac. Either directly or via BTMM and iCloud.
Or relegate the TC to bridge and buy a proper vpn router.. Connect to the network using vpn and you can fully access all network resources as if you were on the local lan. A vpn router is not expensive.