[@Eyeris]
Sooo... this will get a bit difficult. What I am attempting now is an [b]educated guess[/b] of Vaughtar's own weight as this will likely help to derive an adequate predication for the other questions.

I'm gonna use a flat out primitive geometric approach for the first part. As we live in a three-dimensional world, a body of whatever shape whose every lengths are increased by a factor of A can be expected to increase its volume by a factor of A^3. To make this actually useful, I make two additional assumptions:[list][*]The chiseller that created Vaughtar had a sense for aesthetics, so when he decided to make him very tall, he didn't forget about the other two dimensions and Vaughtar has the same proportions as a human body.[*]The material Vaughtar's body consists of when he's not stone is fully comparable to ordinary bone, flesh and blood. So his average density is the same as that of an ordinary human.[/list]
Now I take a human reference, someone that fits his general physique and that I can apply the cubic scaling to. As Vaughtar obviously possesses a general frame and a relative amount of muscle mass that easily matches those of a somewhat professional bodybuilder and for the sake of simplicity and availability of data, I take Conan The Barbarian as the reference. According to google, Arnie at that time weighed up to about 260 LBS at 6'2". So the scaling factor is (82" / 74")^3 = 1.36.

This, however, would only be Vaughtar minus wings, bone extensions, claws, horns, the strange bend between his feet and his knees that makes a part of his legs not contributing fully to his height etc. And there things get way more estimating. The wings can't be just a huge layer of leathery skin put up onto a bony frame because they're an entirely separate pair of limbs on his back and require their own power. This can't be seen on the image, but its the only logical conclusion I can come up with that there is a great bulk of additional muscle that likely spreads accross his entire back where the base of the wings is and partly onto the wings themselves. As a comparison and according to google, a human leg has about 19% of the total body weight, an arm about 6%. I'd take these combined 25% as a minimum for one of his wings - these things are his main means of transportation and have to get him off the ground and with basically no runway at all. That results in a second scaling factor of 1.5 multiplicative with the first one. If I do the calculation and apply rough rounding up for all the things missed I end up with Vaughtar weighing about 600 LBS.

I think that 3/4 of his own weight would be way over the top, but even with less than 1/2 of it he would likely have no problem with carrying even the taller ones of the party, and, as you said, probably two of the smaller folk.

Given Vaughtar being so large I doubt that his flying would be very fast. He also partly lacks a bird's optimization. So I'd summarize it up as very wide turns and a normal speed of perhaps 20mph (what is in the speed range of a condor as ar as I was able to find out). Of course he could climb and reach much higher speeds by nosediving, but that doesn't really count I think.

Holy moly what have I written ? It seems the mathematician in me has taken over when he saw that there were numbers to play with.