Most of the problems you observe have been addressed in version 2 😃

There is the problem of the Hosnian System falling off the map before it is destroyed, but any mention of it after the briefing scene would have to be completely manufactured. I’ve been thinking about how to make them into a sympathetic party, and the best I can think of is building a scene during the assault with various shots in the Resistance base:

Taslin Brance staring at a computer screen (seen in the deleted scenes)
"General, are you seeing this?"
Newly recorded dialogue of a Republic official saying something like "You have our full financial support, but it will take some time to scramble any ships to help you"
Voice of C-3PO (over Leia looking concerned): “Oh my, without the Republic Fleet we’re doomed!”