It's better to buy a cleaning fluid for lens filter. 

as long as the webcam has a standard 1/4 screw mount, it could be used with this tripod. 

Yes and no. Using motion detection it doesn't work through a window. However.... using the timer inside it you can record through a window using it. How? Set the timer to record 4 minutes every 5 minutes for 1-5 hours or whatever time you need it to record for. This is what I do- just make sure you have a SD card with enough memory for the videos- I use a 32 GB SD card, I use it though a window as a security camera for my car....I live in an apartment so I can't hard wire anything and this works great for what it is. 

I don't see why not, remember that the filter goes on the lens, not on the camera. 

I did no use the leather pouch. I purchased a Neewer shoulder pouch. It held everything and easy to get in and out. I carried the 10ND and a 3 ND soft graduation filter.