I created a VR program with 2 8-min 360 degree videos, which when published is over 3GB. Is that a normal size to expect?

Adobe Captivate does not upconvert your 360-degree video files and therefore increase the size of a VR project by a more significant amount than what the video size is. You may wish to apply further compression to your videos before adding them to your 360-degree project. There are two methods to do this that I use.

The more precise way is to use the included Adobe Media Encoder. Add your 360-degree videos and optimise the settings in the conversion process. Experiment with lower bandwidth Mbps and compare the results against the original. Don't change the resolution and you should select the checkbox for VR and select the video is monoscopic. This process will be a balancing act. If you set the Mbps too low the encoding process will reduce the quality beyond an acceptable level, however not lowering it enough will not significantly reduce the file size of your videos.

If you are not comfortable changing the compression settings of your videos you can upload your video to a YouTube account and then download it again when finished. YouTube has excellent video optimisation technics. It is not uncommon to reduce video file size by a 10:1 factor. I have a 13-minute 360-degree video that unfortunately I don't know the original file size but just downloaded it from YouTube to see what size it is. It was 230 megabytes; still quite large for elearning but much smaller than your many gigabyte files.