There a box labeled channel map. Change and save that. If it doesnt work try another and repeat. There are only 4 choices. Takes maybe 3 minutes to change and check if you have to try all three untested mappings.
The channel map is one thing, but everything jumping around like that is something else. 2 things I noticed from the video, you didn't save & reboot before you changed tabs so everything you changed was lost. Also, you are using a FrSky Rx, but selected Spektrum2048 as your serial provider, this should be set to SBUS.
Gremlins ( original) with the femto fc, 6a bullet escs, and 1104 motors can fly on 3s. Mine has been doing so since its second week of life.
Several things you need to know before trying. The tiny jst power connector and wires dont cut it. You have to go to thicker wire and xt30 connector. This means your batteries will have to have them as well.
Second you need to know how to tune a quad using pids. You can smoke these motors and esc in a few seconds on stock pids and 3s.
If you do attempt 3s test EVERY change for 5 second hover, check temps, 10 second hover, check again, if you can get to a 30 second hover then you should be ok to work into flying. Again build up into higher power levels and check temps frequently until you are sure it is set up to handle the extra power.