You WILL spill water so +1 on sealing the stand. If I had it to do over again, I would paint the inside of mine with Flex Seal or something like it so it can actually hold water. Mine is heavily urethaned, so the wood itself appears to be protected but that is only the exposed surface. Every time I spill enough to pool it runs to the lowest point and eventually seeps through. I've had 2 such incidents in the stand over the last 4 years. I'm not seeing any structural weakness in the stand but I assume the floor under the stand is trashed. So seal it up so it can actually hold water inside it. I'd seal it all around up to the level of the doors. In my stand that would hold 15 gallons of water (48X24X3 = 3,456 cubic inches or about 15 gallons). Even assuming 10 gallon displacement for the area of the sump up to 3 inches, if I cracked the bottom of a 5 gallon top-off water container heaving it in there, all the water would be held inside waiting for my shop vac to get it out.
The second area of concern is the front of the tank. You will also drip and even spill water there when you do water changes or clean the tank, or even reach in to spot feed your coral. That frequent drip and spill on my floor there is showing it. I highly recommend a nice looking rubber backed area rug in front of your tank to catch that.
Finally. call your home insurance company and make sure they cover floods inside the house from a fish tank catastrophe. They probably won't cover the tank itself but even the loss of a high-end tank with lots of valuable coral won't come close to the damage even 50 gallons of salt water will cause to your house if something cracks. It's very unlikely that would happen but why even take the risk when the cost will be tens of thousands of dollars? There are more than a few really sad stories on RC about this one.