Quite a dishonest seller if all these potentially catastrophic damages are not shared with you fully. To wilfully conceal these defects is truly low. The cabinet will give way and it is very dangerous.
You are entitled to a full refund imo. If you are willing, I believe this community is going to stand behind you. I have bought defective 2nd hand items and even tank that leaked upon fill up before and the sellers were very steady to refund with no questions asked.
I believe my experiences are the norm rather than the exception, cos the community is tight knit like that. Share the seller, lets see how we can proceed.