Yes, an LPR who is renewing status may be a joint sponsor.

It's unclear what immigration question you may have, if any, without additional information.

Your absences in the US appear to exceed the statutory minimums, coupled with no reasons for the excessive stay abroad. You may be ineligible for...

There is an interview followed by decision. The 7 months refers to interview scheduling and not decision. You may do an inquiry and request status...

You may not unilaterally change USCIS assigned field office. Your attorney would guide you through.

At your DS-160 interview you may make corrections.

You may amend your DS-160 at interview.

With an approved I130 you may file the I485 (Adjustment of Status).

Elevation from current position to higher one in processing time context.

The N400 will not be adjudicated until the I751 has been adjudicated, which begs the question of what's the point?