Hi Steve,
What I have found is that some SD cards come pre-formatted with exfat, and air stash does not like that. So you need a computer to reformat the card. So this is something you will need to watch out for and have a means to deal with.
No problems with iPad 4, it is an iPad, and works like all of the iPads (which is a joy because on android every tablet has a different set of features from one to the next).
Yes, any charge that has a USB port and is powered can charge it. So you can put this in a charger in your car to keep it charged, while others can stream movies or shows from it.
Yes, you can use micro-sd cards if you have the adapter. The air stash+ is designed to hold SD cards. Several of my cards are micro-SD cards but they all come with adapters that I put them in.
I have a camera connection kit but I never use the thing. I don't see why you would need both.
Yes, you can save photos, docs, and other stuff to the air stash. Apps like GoodReader, pages, keynote, etc, can read and write files to/from the air stash.
So, this remaining issue is the format of the card when you buy it. I got a new one not long ago and it had this exfat format. I had to reformat it, so this could be a problem for you. I'm not sure at the moment why it came formatted like this...this was a 64gb card, so that may be the reason. So you have no other means to format the SDCard? I think we need to look into this a little more before you spend your money. I will see what I can find out about this...and maybe someone else can jump in with an answer for this.