Have you actually measured the space between the tires? I have what looks to be the same or close to spacing on my NW Fox Mtn. I only have 2.25" between them. If that's what you have then you won't find any 16" tires that will work. Also you need to find 16" rims with 0" offset. Anything over 0" will cause the wheels to stick out further and the tires could rub on the fender trim.
JMO But I'd go with 15" Maxxis.
You need to check your spacing between the tires before going any further.
Your current tires are 28.3" dia. The Ribs are 29.4" dia. You will close the gap you have now by 1.1". On my trailer that only gives me about 1.2" of gap. Not sure if that's enough.
