One Gallon Batch Sparge Suggestions

Hey best friends.

I've got the gear to make the standard 5 gallon batch, and I have a 10 gallon mash tun. I am a college student, however, and I just can't afford to spend the necessary money for a full 5-gallon-batch-worth of grains, bottles, and yeast; further, I'm more interested in experimentation with the grain bill. For all of these reasons, I want to try my hand at all-grain one gallon batch brewing (strictly stouts for the moment). I also know the various sparging techniques and, admittedly because I am a fool, I care little for meticulous calculations of mash efficiency. I need some expert advice on a few things, and I am hoping someone more experienced than myself can help me!

1.) Is a 10-gallon mash tun (with stainless steel false bottom) too large for a one gallon batch?

2.) Since I only care about batch sparging for the moment, can anyone give me a calculation for the volume of mash water required? Do keep in mind this volume calculation will be used with a stout grain bill.

To clear up any confusion, here is exactly what I want to do:
1.) Grind the grains for a one gallon Russian Imperial Stout batch
2.) Pour the grains into my 10 gallon mash tun
3.) Boil enough water to mash, drain, vorlauf, and the runnings collected be the final wort- and this volume of water is what I am most concerned about.

I need to account for boil evaporation before the mash, water absorption during the mash (lost to trub), and evaporation during the wort full-boil.

4.) Obviously the remaining steps are given.

3.) Anyone have any advice in general for one gallon batch success?

Thanks my good and decent fellow members!