I think you already know that answer. But in case you don't NO, stop using it and fix the problem. And sadly that looks like a transom replacement . JMHO
Allow me to rephrase your question
The back of my boat is about to get ripped off, should I keep using it?
I would say you have pushed your luck far enough, a visible crack like that could fail at any time and I would imagine it won't subtle but just rip right off with a running in gear engine attached to it.
Not a situation I would like to deal with so no, you should not keep using it and if you do certainly wear a life jacket because you are going to go swimming at some point.
I used CoreLite Board last year to replace stringers and transom in my 59 Lake 'n' Sea. Was very easy to work with and I liked it but in hindsight I think I wish I had used exterior grade plywood (not treated) and epoxy instead.
Yes it's more than fine but...very pricey and NOT needed. Properly prepped, installed and maintained plywood transoms will last for decades. I'm guessing this is a Bass Boat? If so..then then there's a 90% chance that you have a LOT more work to do than just the transom.
Because in hindsight I don't believe I'll see any benefit from the extra cost. As Wood always says, exterior grade plywood with proper encapsulation will outlast me. Mine was a 1959 Lake n Sea (known as leak n sink) that wasn't very well taken care of and it lasted 50 or more years. With epoxy on fresh plywood I think my grandkids could've enjoyed it.