I get some seated meditation in a couple of times a week teaching a morning wellness class. We usually end with a short bit of meditation, the only problem is I need to keep an eye on the time, so I rarely get into it!
Sitting down too much is certainly not good for your health, but how many of us will happily sit and watch a film or an hour long TV show? Or regularly drive an hour or more to work?
I think worrying about more than half an hour sitting down is excessive. Just don't spend all day sat down and try to get up at least once an hour to move around. All of those studies are short term responses, people will actually deliberately induce this kind of thing with blood flow restriction training for increased muscle building. As with everything serious health issues can make something unsafe, for most of us, it's fine. The real danger is cumulative sitting e.g. 8 hours a day, 5 days a week for 20 years.
Go meditate for an hour if you want, just go for a walk too, and get a standing desk.
On moving meditation, forms are indeed a great method. Focusing on your movement to get them right at first means a less busy and flitting mind. Once you know it inside and out the brain can switch off and the body does what it needs to. I have found this most noticeable in competition; multiple times I have started a form and the next thing I know I'm finishing it, and I have no idea if I've done it all or done it correctly! I am assured by my friends and the medals that I have!
Deliberate walking can also be a good method of moving meditation, paying close attention to your steps, the shift of balance etc. Anything which focuses your mind and stops it from drifting around as it usually would.
On the flip side, sometimes it is good to be quiet and let your mind wander. At these times you can come up with bright new ideas, solve problems you've been working on, and generally be more productive and inspired than you might otherwise be. Modern life is too full of distraction and both quiet thinking and quiet not thinking have their place.