Wetsuit OWS time v. No Wetsuit pool time

first thing i will say is learn the flip turn, it really helps control you breathing since you must hold it turning thus giving you stronger lungs.

as for wetsuit OWS and pool, theres too many factors to give a great comparison such currents and chop. i swam 12 minutes for 500m when i was able to do it in sub 8 thanks to a good current come race day. a wetsuit will make you more buoyant in the water by making the lower half of your body float up to the surface thus creating less drag in the water thus making you faster.

A lot of variables to consider - sighting and accuracy of course are two big ones that come to mind. Also a proper fitting wetsuit is key. One that doesn't allow enough shoulder rotation can screw you up in a hurry.

Personally, I haven't seen any notable improvements in my own swim times due to the above factors. But the leg buoyancy and confidence boost are nice. My best OWS time was without a wetsuit and was equal to my pool swim times.

When I first started doing tris, I was significantly faster in my wetsuit than in the pool ... like 20-30 seconds per 100 yards. I assume the buoyancy provided by the suit was correcting some horrible problem(s) with my form that slowed me down significantly in the pool.

Now that I'm a lot faster in the pool, the difference isn't as dramatic but I've swum in OW without a wet suit a few times when I thought I was doing a race that wouldn't be wet suit legal and I was about 7 min. slower per mile than my slowest time swimming in that same water in a wetsuit.

I mostly agree with the others, but my personal experience and observations have been a little different.  The amount of time gained with a wetsuit will actually vary based on swimming ability.  It will help a weaker swimmer who struggles with sinking legs much more than it will a better swimmer who can keep their hips and legs high.  10 seconds / 100 is about the average, but a beginner swimmer with a lot of flaws may gain 20+ seconds / 100 while an elite swimmer's improvement may only be in the very low single digits.

At 1:30/100 sustainable pace, you're a decent swimmer by triathlete age group standards, so I'm guessing your balance, streamlining, and stroke technique aren't too bad.  Just going by that, my best guess is that you would gain closer to 5 seconds / 100.