You need to use 'G-Metrix Sync'. Button is right next to 'Activity Start Time'.
I'd probably try to start the beginning of the race.
Use the slider on the left to pick the frame when the race started, then do the same thing on the right.
I agree, the alignment dialog is close to impossible to use with dozens of laps and multiple videos covering these laps...
I've given up on using this data for lap times as my GPS readings are sporadic at best. With multiple video sources though and syncing up with the data, my solution has been to export the data to a PNG sequence and then managing the syncing myself. I export one copy of the original video with the data overlay (with no editing or anything so it's synced) and then use the audio from that as a marker to sync with the other videos.
My VIRB GPS data is fine. But the alignment, as you said, especially woth addtl non-VIRB video sources is unusable in VIRB Edit.
I use Davinci Resolve to actually make my videos. It's free and seems to be pro-level quality. I'm now only using VIRB Edit to generate the PNG sequence and a low-quality video just to use to sync them in my main project.
That said... I LOVE that it does the PNG sequence thing. That single feature makes it a game-changer for me.