The scale playing indeed looks hoppy, as yourself and others have already pointed out.
Again as noticed by others you have a good starting point with that tremolo example, and you should start trying to play phrases that work with your “tremolo motion”.
I’d start by trying phrases that exclusively change after downstrokes (“DSX phrases”), then try some that only use upstroke string changes (“USX phrases”). Check which option feels most comfortable: that will gives us some insights on what your “primary motion” could be.
To get started and keep things simple, even just moving between 2 adjacent strings could be sufficient.
Let us know how it goes!
PS: your “single string playing” video links again to the scale example, so you can edit the link when you get a chance. Knowing the current status of your single string playing will certainly be useful additional info