the 5th wheel I'm looking at has a dry weight of approx. 16k lbs. I figure that living in it full time, I'm going to add quite a bit of weight to it with just my normal everyday stuff. If I could find a 3500 SRW with 5k of payload and probably 25k of available towing, I think that would work but so far I only saw DRWs able to get there.
Once you decide on the exact fifth-wheel RV you are going to purchase, get its maximum wet weight and size a tow vehicle to the number. You are not going to find an SRW with the payload and tow numbers you stated.
When I was in your position I did a lot of thinking and research. My wife and I spent a summer visiting campgrounds and talking to campers about campers and tow vehicles, it was quite an education. You want to know what you are getting into before you buy because once you buy, you are stuck with your decisions.
For me, it came down to SRW versus DRWs. I took the time to understand the benefits of a dually as well as the not-so-good. Our desire for camping was traveling our country and seeing the sites. Having done this by car travel I realized site-seeing venues can be very difficult to park in with a car let alone a big-hipped vehicle.
I took the payload and towing numbers for a RAM 3500 Longhorn Cummins and my wife and I looked for a fifth wheel that would fit the tow vehicle. A 3500 SRW is very generous with payload and towing numbers and we had no trouble finding an all-season 40-foot camper. We bought a Montana 3790RD.
Everyone's situation is different, what are you willing to give up versus what can you live with. In our research, we found very few DRW in the campgrounds, and when we did, they were pulling tri-axle toy haulers, something most don't opt for. DRWs are popular with the big horse trailers and the construction/hotshot crowd.