Q1: Yes, Alamy is a non-exclusive agency.
Q2: Don't know, but your search is as good as mine.
(Remember, though, that if submitting the same RM files to multiple sites it's your repsonsibility to keep tabs on what has sold and for what purposes, in case a buyer should want specific rights on an image.)

There are many small RM Agencies out there. It may take you a while to figure out whats good for you. Some sell more and some less. Sadly there is no easy guide to get installed in this market, meaning, no such thing as the "Big four". Actually I would really welcome if one of the bigger RM or Trad Agencies would open up and modernize its workflows just as Alamy or the Micros....

That's useful, thanks

I was beginning to wonder if it was worth it.

I'm with a few RM distributors such as Robert Harding and Arcaid which have started to bring in some cash. Getty is so far the one that is outshining everyone else at the moment and I've been trying to get as much in there as I can. Currently satt at just over 1000 images both RM and RF with the majority at RM.

Probably best for the moment [1] to sit it out at Getty, since you've got RM there.
The main exception would be if you have very specialist images, in which case I think the way forward is to look at publicatons which use your specialism and see which agencies, if any, they use. You might find that they don't use agencies and sent wants lists out to their selected suppliers directly.

[1] Bit with a weather eye out for the future. The bigger they come, the harder they fall.

I have a question regarding RF sales:

how are your RF sales on Alamy??

Well, nonexclusive RM is as good an oxymoron as military intelligence.

The reason, why the agency takes as an image as RM, is that they can track and police its use.
By the way, RM used to stand for Royalty Managed.

I've only heard it as Rights Managed, never Royalty.

Amazing what you can learn on the Internet forums. 

http://www.alamy.com/contributor/help/image-licences.asp

Alamy: Rights Managed Licences:

There are 100's to decide on before choosing the most appropriate ones for you; that's if they'll accept you as a contributor.

http://www.cepic.org/directory/member_agencies

Above will give you an idea of a selection. Some will give great returns, others will be like Crestock. Methinks some research is in order, it's far from easy to choose a good agent and make good sales; although they do exist.

Oldhand