I don't have a statistical breakdown handy. However the reports where what is seen clearly looks and behaves like an intelligently controlled object, and in particular the radar/visual reports.
If our senses give us the impression that there is something solid in our field of view, there is a very high probability that there is. I'm not sure what you mean by "non-sensical and surreal", but active camouflage can explain a large amount of strangeness.
That depends on what you mean by "serious theorist". If we are to make that synonymous with "scientific theory" and investigation, then I don't think we have any really good examples. The closest might have been Hynek, but if I recall correctly, although he may have been sympathetic to the ETH, he never made an explicit endorsement of it. If we are using the word "theory" in a more casual sense, I'd say that Friedman is a serious proponent of the ETH. He is a genuine scientist who has worked on nuclear propulsion and who often points out why the reasons the skeptics give against interstellar travel aren't as sound as they'd like to believe. I'm personally a proponent of the ETH to the extent that they don't come from Earth, but their exact origin is still in the realm of speculation.
Regarding speculation in general, I don't know any ufologist who doesn't engage in speculation. However speculation isn't a bad thing so long as it's kept in that context. My problem is when speculation or even personal experience turns into absolutist statements that aren't based on sufficient logic or other evidence. Examples of such are the abductee/contactee cases. Even if these people are having genuine experiences, I don't think that simply taking the accounts at face value is wise. The overwhelming nature of such an experience could conceivably lead a person to blindly accept what they are being told as true, when in fact it could be some form of disinformation. Similarly messages that seem to be based in fact might also be used as a sort of propaganda tool.
For example, one of John Mack's cases involved aliens displaying a series of beautiful natural wonders juxtaposed with the environmental crimes of humans. This is no different than eco-propaganda. I'm all for environmental responsibility, but at least our own exposés on nature also show the savage side. The lovely and graceful impala standing in the tall grass will get eaten by a lion, the beautiful snow capped mountain can erupt and spread death and destruction over a wide area. Nature's fury is nothing to be trifled with and most of our efforts have been to improve our otherwise weak ability to protect ourselves from it, and to advance our civilization. But the alien messages never give us credit for that. Meanwhile they allegedly fly around in giant mother ships casting judgment without sharing any of the technology that could help us drastically reduce our eco-footprint. In the face of these things it's only natural for any rational person to be wary of the claims. Still, I don't think it can be reasonably denied that something strange is going on.,
