What sound card do you have? Use those picture and video skills to post a picture of your soundcard. Is it an internal soundcard in your computer? Those almost never work right for REW or audio programs.
Start with the preferences main screen and make sure everything is working before going to anything else. You have a couple of things. Set the SC you are using as default in your control panel. Keep the control panel open while you try to figure this out. In REW you have a couple of things. You have the main measurement channel you can switch between right and left with a check box. You have the drop down box that should show all of your available inputs and outputs. Make sure those are set to what they should be. Try a few of them if you aren't getting a signal. Also you have your output level and your input level. Run the check levels routine until you can get the signal up into the green. You should be able to clip your input with a loopback. (Most any SC can put out more voltage than the input can handle. If you can't get up above -40 or so then something is wrong with the set-up. Did you turn up the output level in REW to the max?
I wouldn't worry about posting max spl #'s below 30hz off of a Ratshack. Anything with a generic cal file with corrections of 30 to 40db which may or may not even be in the ballpark for that particular meter, I wouldn't take too seriously for spl measurements below 20hz. Those correction values seem WAY high to me. I remembered them being about 18 to 20db all the way down at 10hz. I could be wrong though since I never used a RS meter for more than a day. Anyway we want to seem some 3-200hz sweeps at a moderate volume of maybe 95db. Hell I'd like to see some without any correction factor applied for the RS at all first. We can get into loading a cal file into REW later. Also make sure measure with the meter where your head usually is when you watch a movie.