I've been abusing Ikelite housings for 6 years now. I drag the thing around in caves, toss it under boat benches, and giant stride into the water with them.
Acrylic can craze, but that's a very slow failure mode and I've never personally seen it. When I have heard of it, it was repaired during annual service included in the ~$150 service fee.
Your port is different than the larger SLR housings, which are held on by 4 flimsy plastic sliding latches. I have broken a latch once, but those are only really providing any support at the surface. Underwater, you have tons of pressure on the dome port that is holding it shut, you could probably take all of the set screws out, and try to pry the housing open, and never succeed...I say probably, because it depends on depth and your strength...but it's a lot of pressure!
In your case, the set screws are not directly holding the port on. They go into a "trench," such that even loosening them so one or two entire threads is visible, should still leave a portion of the screw in the "trench" and then it won't come out. That is, the ability of the port to come off is a "yes or no" type of question, it's not like loosening it somewhat, will allow it to come off with some amount of force, and loosening more, will allow it to come off with a little less force. There will be a very small range where it could be removed, and then just past that, the force to remove it will grow exponentially to be equivalent to the amount of force required to break the plastic.
Surface area is not really important when it comes to flooding. Having more buttons is a risk, but that is typically a slow failure point. Get the housing serviced and it should be fine. I've never had a button leak and I've never gotten a housing serviced.
The two latches on the back are again only for the surface. Once underwater, the water pressure provides more closing force than the latches by orders of magnitude, and the housing is going to be fine until the rated depth, and then some.
The vacuum systems are nifty, way, way way nifty...but expensive. Then again, DAN insurance on the housing is expensive too, and you have that, right??? But these are cheap, and they'll catch a leak within seconds of being underwater. I've seen them save 2 cameras!
Underwater Camera Housing Leak Detector - Home Page
Personally, I've had my Ikelite housing leak 3 times. Every time was due to me not sealing the rear seal properly. Never damaged anything in the housing because I caught it at the surface within moments of the housing seeing water. I've only seen one housing fail underwater, and it was in 5 feet of water when the user bumped a latch. Their Nauticam latches don't work like ours and while they are easier to use, they are also easier to bump and unlatch, and in 5 feet of water, you can do that. And their built in leak detector failed from the water, so the housing required $500 servicing. Your Ikelite housing likely would not have flooded in that way because the latch design is different, nf it did then it probably would have been fine, and the leak detector is $36 instead of $500...
Can you tell that I like my Ikelite equipment?!? Now I've had one DS125 head flood due to a crack in the plastic, one DS125 battery pack flood due to mis installed oring (my fault), and one DS51 battery compartment flood (probably my fault), and one EV Manual Controller flood (those things are pretty old, just it's time, I dragged it through a lot of caves). Ikelite has taken a lot of my money, and atleast one product design idea. But they are awesome.