1. SCLogin trying to load the bootstrap file regardless of JFBConnect's setting looks like a bug. You can try the following code to fix it.
In /modules/mod_sclogin/helper.php around line 72, replace
if($this->isJFBConnectInstalled)
with
if($this->isJFBConnectInstalled && JFBCFactory::config()->get('jquery_load'))
2. The inclusion of sc_bootstrap4 instead of the correct sc_bootstrap5.css was a bug that was fixed in the 9.0.170 release.
3. DOM IDs - I've added an issue to our tracker to fix this. Should be an easy thing for the next release.
-Melissa