How difficult is it to travel around Moscow, knowing only English?

Not very difficult.
It is easy to get from the airport to a hotel and to major tourist sites. Some taxi drivers speak English and if they don't, they will at least know those popular locations.
Taking the metro around is also a good option, but not as easy. There are very few maps of the metro system in the stations and all station names and announcements are in Russian. But if you have a metro map, check the color/number of the lines and count the number of stations you should be able to get around pretty well.
In hotels and cafes or restaurants you should also be able to find people who speak English and the popular restaurants have English menus, so overall I don't see any issues if you stay in central Moscow.

What is the best way to obtain a Russian tourist visa?

You don't need a company or site if you live in the following cities that have Russian Consulates:  San Francisco, Houston, Washington DC, Seattle, or New York. They also have their processing partner ILS, which makes the process pretty easy.

If you don't have that option, "A Briggs" is pretty good choice. But realize that most of the work these companies do is a) receive your passport and app in the mail and b) make sure you filled it out correctly. It is between $30-$60 per person in addition to the ~$150 that Russia charges you for applying.

Things you'll need:

  • The name of the place you're staying and dates
  • An official invitation (you get get these online for about $25 if you don't know someone living in Russia.)
  • Completed online application, also print it.
  • Passport photo (to stick on the application)
  • Passport valid for 90 days after your exit.

If you need help with forms and stuff, my wife and I wrote a very detailed step-by-step analysis of how to do the entire application process, if you're an American. You can find it here: http://www.est2010.com/how-to-ge….

What is the best US debit card to use internationally, specifically in Russia?

Fidelity Visa Gold Check Card is the best international debit card. I have not used it in Russia but used it Mexico, UK, Spain, France, India, Japan and Australia.

  • It has $0 fees for  ATM withdrawals (any Visa®, Plus®, or Star® logos ATM in the world). Any fee charged by the ATM (upto 4 transactions per month) are also returned back to you if you use Fidelity Cash Management Account
  • It has $0 fee when used internationally as debit card. (there is a 1% fee charged by Visa on all international transactions that still apply)
  • There is also no fee to maintain the card.

What is life like in Yuzhno-Sakhalinsk, Russia?

Pretty small and boring city. There are a lot of foreigners there as you know so they are the best source of such kind of information (I am not living there for 6 years). Skiing (especially mountain skiing) is very popular, we have a local small ski resort called "Gorniy Vozduh" ("Mountain Air") which is located right by the city border at east. Lots of beautiful nature spots (lakes, capes) around  the city but it's better to have someone to be a guide. Right now there is a special fishing season called "Putina" (not in honor of Putin) when salmon comes back to it's origin rivers so don't miss a chance to taste salmon and caviar for sure.

How safe is Moscow for foreign visitors?

I have felt pretty safe in central Moscow and have had no problems even walking around at night. I haven't had any problems with Taxis or in the Metro either. Many people also stop random cars for a ride both during the day and at night and that seems reasonably safe as well, even though people recommended to not take a car alone at night. Not speaking Russian doesn't make it less safe in my opinion.
That said, there is robbery, organized crime (which shouldn't affect tourists), and terrorist attacks like the recent metro blast, so things can happen if you are unlucky.