I agree, your case is very intelligently put forward.
1.) The Colts organization suspects Luck is gonna miss some games... and despite what the fan boys here say, Luck is going to look rusty when he returns for a few games or maybe the whole season. (whole season being an extreme, but possible.)
2.) The Colts organization knew that without a healthy and well practiced Luck this season is gone... Doesn't matter if the defense plays like the 85' Bears or 15' Broncos. So, they allowed Pags to stay as the lame duck with the hope next year would bring some better replacement options.
1.) I don't think not bringing in another qb means too much. Tolizen may look bad, but really how many backup qbs are available on the market that can fit into the schemes the rest of the Colts offense has been installing all off season? Available qbs this time of year are available for a reason.... They suck.... I think the Colts would rather have guys who suck that at least know the playbook.
2.) I don't know think the Colts are super worried about draft position. Teams like the Patriots show that having staff that can actually evaluate talent is much more important than your draft position. Although, I won't lie, tanking a season to get a top 5 draft pick to trade for a bunch of later round picks seems smart. Increases the chances your talent evaluators will actually pick somebody who can play.
I am unsure -
My feeble mind isn't smart enough to follow the ins and outs of cap space etc.... I have no clue what any of the new free agents contracts mean.