Left tackle. It is arguably the second or third most important position behind quarterback and/or defensive end.
Tyron Smith missed games but was dependable when he did play for the most part. Blindside quarterback protection is crucial in any offense Dallas puts on the field.
Defensive tackle.
Jerry Jones will do just that. Kinda makes the question moot.
Yes, preferably during the first two days of the draft. It is a practice the team should have implemented for every second or third draft during the past three decades. Jones wants Trey Lance to be Prescott's eventual successor. However, I highly doubt Lance will be as good or better than Prescott has been.
Leighton Vander Esch. Love his heart but he is done.
Michael Gallup. Not nearly the wide receiver he used to be.
Jerry Jones negates my third and final suggestion.
Risky but I would go with Jonah Williams, tackle, Cincinnati. Williams switched to right tackle when the Bengals signed Orlando Brown but he could transition back to left and do an above average job in my opinion. The acquisition would not stop the front office from addressing offensive line early in the draft (if they chose) but it would lower the 'need factor'.