Quoting away, sometimes out of order....
First, about detection of dark matter:
Well, some of the suggestions have ways to interact other than gravity. WIMPs, for example, also interact through the Weak nuclear force - and with a large enough detector, you might catch them through such interactions.
Absolutely! Although, to be honest, people use WIMP to mean anything with a weak-strength interaction, not just the weak nuclear force any more. And these interactions with the Standard Model are reasonably well-motivated. But that part has always been a bit of a guess; maybe there's a whole dark sector with weak-strength interactions and even weaker interaction with the Standard Model. Or DM might interact relatively strongly with the Standard Model but not with the detectors we've built for some reason (yes, I can give some good ones if you want to know). My point is that, while experiments are currently excluding a very interesting part of parameter space, interactions with the Standard Model are not at all required for cosmological dark matter to work. In any case, this is a very very active area because there are a number of hints that we may actually be starting to see some signs of dark matter.
Or one could catch something else and because the interaction is so weak, one could assume it was what they were looking for as opposed to what it really is. It's an extremely hard science at this point.
Yes, it is, and the claims of possible detections, some of them very strong, face even stronger scepticism. People know how hard it is and that there are a lot of pitfalls. We're talking about extremely small signals, and miniscule amounts of radiation, etc, cause problems. No one knows this better than the people running the experiments. The results are subject to A LOT of scrutiny.
How about the Cuspy Halo problem? CDM is the simplest explanation for DM, but the theoretical solutions to this problem require at least some type of an adjustment to CDM models. MOND doesn't have the Cuspy Halo problem TMK because it's a direct outcome of CDM. Pilipenko, Lukash, et al just released a new model a few months back that might solve the problem, but that doesn't mean that the problem is definitively solved yet, correct?
Problem, what problem?
Kidding, kidding...
Let me explain this for our other readers before I respond, since it's clear you've read a lot about dark matter. I should also mention that the wikipedia page on it isn't very good in that it relies on just a few authors (including at least one who is a noted MOND proponent) and doesn't really get at the consensus. The issue is that simulations of the formation of galaxies using plain vanilla dark matter (and other standard assumptions) suggest that dark matter becomes extremely concentrated at the center of galaxies. This is called a cusp. However, observations of some galaxies suggest that there is no cusp, rather that the density tops out at some maximum value. This is the origin of the "cuspy halo problem."
Here's the issue with the problem. First, it's tricky to do observations of dark matter halos (since, you know, dark matter is invisible), and, while people agree that there is no evidence yet of cusps, most observers don't think the observations are good enough to say there is evidence against cusps yet. At least not in all types of galaxies -- small galaxies called dwarfs are typically accepted not to have cusps. But the observational situation for big galaxies, like ours, is far from clear, and there could, in fact, be strong cusps still. On the other side of the coin is that the idea of cuspiness comes from simulations which take millions of CPU hours but do not yet include all the physics. In particular, it's only recently that simulations have started to go beyond just the gravity of dark matter and to add normal matter, which does things like make stars, cool down, etc. This can have different effects on dark matter, which might end up making the dark matter more or less cuspy, depending on exactly what happens. It hasn't been worked out well enough yet.
There are lots of online video classroom lectures and other presentations on the Internet these days. Obviously, nobody is up to speed on everything being discussed, but then again, it's not a complete vacuum either.
But those video lectures are not representative of the experience of being a grad student in physics, or any of the hard sciences. You were questioning how actual practitioners thought, and go about their business - video lectures don't show you what and how we actually learn, or how we are taught the activity of doing science.
No, but they are representations of what is being taught to grad students, the statement of yours which I was responding to.
I have to go do some work now, so just briefly: compared to the number of graduate programs in the world, there are very very few graduate course lectures available on-line, and only a percentage of those would relate to dark matter or anything similar. Also, the most important part of graduate education doesn't take place in the classroom but in meetings with supervisors and on your own reading, doing homework, or doing research (yes, grad students are important researchers). What that means is that, while even cutting-edge subjects might be presented in a "here it is" kind of way in some lectures, the evidence is also presented, analyzed, and critiqued. That's part of what you learn to do, hopefully even before grad school.
