Yes he can!
Read the codex
Space marine captains are very underestimated in the game. A captain is an extremely versatile unit. The list of upgrades a captain can take is half a page long, making them very easy to incorporate into any type of army. You can take anything from terminator armor, to jump packs, to a bike. They are also very cheap, only 100 pts, making them one of the cheapest HQ choices if you are just trying to fill in your HQ compulsory. Hope this helps!
Its in codex space marine under HQ
A space marine captain costs 100 pts, but there is nearly half a page of upgrades to give him.
Yes you can, 10 of them in fact, so long as they are in regular Power Armor. Marines in Terminator armor are too big to fit into a Rhino.
Yes you can.
Equivalent to a full bird Colonel in the US Army.
15 Points in addition to the cost of the Captain
It depends in what kind of terrain you want him to be in, theres grass, rock, lava, dessert, dirt, etc
The type of space marine armor is important. It depends on if the armor is from Warhammer or StarCraft. If it is from the former, then the reference book published by Lexicanum is invaluable. For StarCraft power armor, Blizzard publishes several art books with schematics.
A space marine captain, 10 tactical space marines, 5 space marine terminators, a space marine dreadnought, a ork warboss, 20 ork boyz, 5 nobz and 3 deffkoptas!
Yes, Space marines can take off their armor. They stand roughly 6-7ft tall out of it and 8ish in it. When out of armor they wear simple robes. They train, eat, sleep and pray in and out of armor. The armor does connect into the marines body, at the moment of connection the marine knows what has happened to this armor. The same goes for weapons such as power fist's.