I am not sure the FW-1884 control surface plugin will work without Firewire. I think I tried to do what you want years ago with a motherboard with a poor firewire innterface and could not get it to work with the plugin. I pretty much have to select FW-1884 Control port in the Control surface selector to get mine to work. You may be able to use ACT to assign controls via MIDI but you will never get the total functionality of the firewire interface.
If you had a deskptop PC, I would suggest a $25 Firewire card but with a Surface Pro, I dunno.
The 1884 is picky about interface chipsets. It wants a TI 1394 chipset board and a legacy 1394 driver.
Microsoft released a signed legacy 1394 driver for win 8.1 a while back but not sure what the Surface Pro has for I/O. If you could find a USB-2/3 to Firewire adapter with the TI 1394 chipset cheap I might start there. An express card to firewire may be better but not sure you have this option.
I know folks on the forum have commented about using the 1884 as a control surface only (no audio) but AFAIK they still were using the Firewire interface.
One thing you may want to try is to use the 1884 in Mackie HUI emulaion mode rather than the native mode. THis may allow you connect to sonar as a control surface only via MIDI. I know this works thru firewire but you will have to try it with MIDI only.
Google "FW-1884 Mackie HUI" and you will get to the Tascam doc which describes this. It is all still on the Tascam site.