I've owned all three versions of the X-Pro series. Overall, I found the XP2 the best. It's much more a professional grade camera than the XP1 is. I personally returned the XP3 after a few weeks. Though the EVF is better than that of the XP2, the OVF (that's why you use an XP) is actually not as good since it has only one magnification level (XP2: 2). So, it struggles with lenses wider than 23mm or longer than 50mm. You just don't get the frame lines wider than 23 or the magnification longer than 50 to work well with the OVF.
Don't bother about titanium top plates and sub screens with film box logos on the XP3. These are just gimmicks. In terms of IQ there's hardly any difference between the XP2 and the XP3. In terms of durability the XP2 turns out more reliable since it lacks the strange (for me: useless) downward folding screen. As it turns out, that is an Achilles heel of the XP3. There's even a class-action lawsuit in the US against Fuji for that.
The weak spot of the XP2 is weather resistance. The front- and back dial as well as the on/off collar around the shutter release button are not too well-sealed. So be a bit careful with heavy rain or snow. The XP3 is not better on that subject. It's just that its dial click function feels less mushy.
$600 for a good XP2 is a very fair price. Don't worry about the 13k actuations. That's less than 10% of what Fuji claims as a life expectancy and generally cameras go well-beyond that.
As you mention using MF vintage lenses on the XP2/3 you might also want to consider a XT2 or XT3. Though no 'rangefinder-style', these are great little cameras with a similar IQ. The advantage of the X-T line is that they have a better EVF with higher magnification. That will make manual focusing easier than on an X-Pro camera. Generally, they're also a bit cheaper pre-owned than the X-Pro range.
