OK, here's what I know about what you asked about.
(1) My older 240's (1975, 79, 81) had black plastic console covers and door pockets. Never a crack or failure. Black seems to be tougher than the other colors. Get that black one on eBay and paint the door pockets black to match.

(2) The hole you ask about is the space where pre-1988 240's had their seat belt anchors. When they switched to cable-to-floor anchors, they just put a liner thingie in the hole and that's it. You can store anything you want. I keep a folded up paper towel in the bottom to soak up whatever spills in there.

(3) My 1983 had bolts welded to the floorboards for the cable-to-floor seat belt anchors. They were plugged up, and all my pre-1988 240's have the anchors in the console, and the wider seat belt tips. I think Volvo realized they were paying too much for the wide tips and changed to a type more widely used just to cut costs.

(4) The top of that plastic housing takes just a little to break it it. I have reinforced and repaired one, it's a PITA.

Good Luck,

Bob

:>)