Your comments

Sass is thoroughly supported.  Just install the Sass packages.

Not really a workaround, but one option you might want to enable:

"scroll_past_end": true

This allows you to scroll past the last line of code in a file.  Scrolling past the end would keep the code completion dropdown from getting cut off.
I think it would be fine to simply place the cursor back on the same line as before even if the content of the file changed would be the easiest.  Trying to make ST use diff's to figure out where the previous line was if it moved in the case that the content changed would be a LOT more work.  That would be nice someday but imo just the quick and easy solution would be better in order to push the feature out sooner than later.
I'm pretty sure embedded code is already supported in syntax highlighting.  Whenever I'm editing a PHP file that contains both HTML and PHP code, the PHP code is treated as embedded code and is highlighted appropriately.
I never found a solution beyond disabling the embedded source settings from the theme file per Phalkunz solution below.  I really like seeing an alternative background color for embedded source, that doesn't really work for me.  I've just been living with it up to this point.  Wish I understood the theme file better to understand how to fix it.  I tried adding a cursor highlight color to the embedded part in the theme file but it didnt' work.
I can appreciate that approach, but I enjoy seeing embedded code with a different background color.

So is this a bug?
Okay so I figured out in the Cobalt.tmTheme file, under the section for Embedded Source, the PHP background color is specified.  I figured that I could just add in a lineHighlight color for this section so that it forces the proper highlight color, but it doesn't seem to work.  It seems to just ignore it.
Ya, this feature is in the pre-v2 Sublime Text.  It's very nice and hopefully can be added back in.