Q1.
I'm using virtualized config.wtf files, which is a feature IS Boxer offers. Basically have medium settings on the main, and minimal on the slaves. I don't bother with anything to change the settings on the individual clients as I switch from one to the other. But I believe there is an addon that can do this; Zanthor mentioned it in one of his posts.

Q2.
You only need one installation of warcraft. The only advantage of multiple installs is different game options. A virtualized config file takes up a lot less space then another install of warcraft. However, you can do Symbolic Links (I used this tool: http://schinagl.priv.at/nt/hardlinks...kshellext.html or use the MKLink command), where you copy the entire folder, but delete the Cache, Data and Interface folders, and then link them from a full install. I'm running five instances off of one install, and not using symbolic links anymore.

Q3.
IS Boxer has strong mouse broadcasting options. You can broadcast the mouse with Hot Key Net, Mojo, Octopus, and probably other software options too. You could mouse turn, but generally mouse broadcasting is to click things such as portals or bonfires, or accept on a dialogue box, and for ground target spells. Follow is generally far superior for movement.

Q4.
Jamba is not essential, but it is extremely handy. It is quest mirroring, where any option you pick with an npc, the slave will do the same. You can have the slave take the same rewards from quests, or force it to have you pick on each toon. You can set it to auto buy reagents when at a vendor, to sell gray quality items, to have the slave take the same flightpath as you. You can have an indicator, showing slave/master follow status, experience into the level, current health. You can have warnings when low on health or mana, and can customize this for a large team with a message like, "Press G4 to Heal Bob". A very useful boxing addon, and highly recommended.

Q5.
Log into account management and send yourself an invite; you won't need a new email, I used the same for a 5 account RAF chain. Use the emailed information to create the account, and then upgrade with a retail copy of the game. If you are ditching the account, just go with Classic Warcraft. If you're keeping the account, go with a Battlechest. In the case of ditching the account, you can create a Human/Orc on the ditching account, and if need be summon your Draenei/Blood Elf to zones that disposable toon has access to. I'd recommend leveling two sets to 60th, per link in your chain (in your case it is one link, so level toons in pairs); that will let you boost toons to 60th from 1st. Also when boosting, get a toon 90% into the level, say almost 3rd or almost 4th. Then grant levels, and you'll be 60th and almost 61st.

Q6.
If you care for a Zhevra mount (it is an achievement too), pay for the 2nd month on the disposable account. Then one toon on the existing account gets the mount. RAF goes for 3 months, so a game card is a decent option as that gets you the free month and the mount, and 2 months to RAF with. You have the option to pay for the 3rd month if you like/want the time.
You could also go with one keeper account, and two disposable accounts. Chain them together... A -- B -- C. Include a Prot-Pally or Feral-Druid on A (keeper account). Level the first set as three toons together, and take them through Outlands (or possibly solo outlands with only the keeper toon). Then use the Pally/Feral, to "boost" B/C through instances, and they'll get RAF experience because of being grouped together. If you boost three sets of toons (plus the initial three toons as a team), that adds up to: A x1 -- B x4 -- C x4. A then gets two toons from B and one toon from C (cascade granted levels). You can boost toons from 1st to 60th, in a weekend quite easily.

Q7.
With two toons, just about anything will work. However, I'd recommend spec'ing for DPS. If you have two pallies, go with both of the as Ret. Or possibly Prot + Ret, once you're high enough for Holy Shield. You can use both of them to heal during down time, but a healer spec is pretty much a waste. Just about any combination of two will work.

Q8.
Boxing can be extremely fun. There's a high probability that if you try it, you'll want to permanently go with 2 or 3 toons, which eventually leads to 5 toons. Be aware of that, going in.