You only need to make them snug. I doubt you could damage tires when you think of how much weight a TT imposes on the contact patch area on the ground. The X-chocks have a bit of a radius on the pads.
If you are anywhere near the border, use a "mailbox" on the US side of the border and go pick it up. You could have bought those here for example for $55.88 (plus shipping):
MakariosRV $236 for a pair of them is highway robbery.
Buying any RV parts at a local RV dealer is like dealing with the Mafia. You can buy RV stuff on the internet for a fraction of the price. We have purchased a ton of RV and household stuff on the internet and get it shipped to Blaine, Wa. We've saved maybe several thousand $$ by now. We limit what we bring back on a short duration trip to $200-300 for each of us and never get pulled over to pay duty or taxes. The only time we've ever been pulled over is when we had a $500 computer. If you're not near the border, this isn't an option though.
If you do happen to be near the border, I recommend getting a Nexus card. We usually get through very quickly.