I haven’t opened up the new 16” models yet, but I can tell you I don’t have any problems opening the 13” & 15” models which use the exact same design.
You appeared to have pried a lot more than I do! Did you follow this guide? As well as use the same tools?
MacBook Pro 15" Touch Bar 2018 Lower Case Replacement
I personally use a much larger suction cup as well as make sure I slide the bottom cover forward so the rear clips and mid studs becomes unlatched. The trick is getting the tabs to clear the slots in the middle this is where the suction cup (and your strength) is important! Pulling up the plate enough so the tabs slide out as you slide the cover forward. I use the 6~8 plastic guitar picks to hold the lid out of its uppercases slot-way.
Focus the prying to the bottom edge so you can slide the bottom cover over the uppercase’s slot-way. Once I get the bottom clear I slide the pick from the corner point up the side about an inch on each side and 4 or 5 along the bottom and pull on the suction cup downward Not Lifting!
Placing the bottom cover on is just the reverse sliding the rear in first, I’ve found only sliding it in about a quarter of way in then snapping in the studs so the stud is not bottomed out in the clip that is what damages it.