Imperial Remnant questions

[Star Wars Fan]

1. why did Pellaeon retreat to the outer rim after the failed atack on the Jedi Academy on Yavin IV? There was Imperial Territory nearby, which the 17 ISDs could repair and Pellaeon could unify, but why didn't he return to the Deep Core. the VSDs did. the Deep Core had a advantage, thousands of worlds which the New Republic didn't know about. it was resource-poor, but it was still sustainable. was there more resources in the Outer Rim? was it because Bastion was there?

2. Bastion was continually moved. after Coruscant, was Bastion the new capitol, and Imperial High command (in the Outer Rim) there? it was heavily defended, so how could they move it so many times?

3. what forced the Imperials out of the Deep Core?

4. isn't the number of ships and systems under the Remnant's control low (only 1000 worlds, 200 ISDs for 4 sectors). wouldn't there be more systems?