Yes, you don't actually need FS1 to install FSPort. From a legal/ethical point of view, though, I think it's better to own it, since FSPort is based on game data extracted from FS1.
As for ST:R, I actually installed it quite long ago using Turey's automated installer (
see here). It seems a bit outdated though (at least, its wiki page is, since it indicates a 3.6.10 build, whereas the latest version of FSO is 3.6.12).
I don't have my install with me right now, so I can't check, but I'm pretty sure ST:R is supposed to be installed in its own folder inside the main FSO directory. You'll need FSPort installed too. Then, in the launcher, select the mod Silent Threat Reborn, and it will automatically grab some data from the FSPort directory and, if you have them installed and activated, the mediaVPs directory. To do so, the mod uses the file mod.ini in the mod directory, which tells him where to search for data. It seems that ST:R (and probably FSPort too) is designed to use the 3.6.10 mediaVPs, which should be located in the mediavp directory. If you want to use the newer and improved 3.6.12 mediaVPs, which should be installed in a dedicated directory (mediavp_3612) you can alter FSPort and/or STR mod.ini files to replace mediavp by mediavp_3612. You can find an example at the end of this thread :
on HLP.
This is a bit complicated so the bottom line is : STR should be installed in its own mod directory, and you will need FSPort installed as well. Everything should run fine just like that. But if you want improved graphics without too much hassle, install the 3.6.10 mediaVPs as well, in a directory named mediavp, and that's it, no manual file editing required. If you want even better effects, install the 3.6.12 mediaVPs in a directory named mediavp_3612 and edit the mod.ini files of the mods you want to play with those newest mediaVPs.