Well, the forum tortoise id god is Danny (egyptiandan). Send him a message.
Could you take a picture of it's plastron (belly)? That would help.
Depending on what species it is...you can then pick out an appropriate substrate. The pellets in your picture are not the best idea. I know that stores try to sell them as tortoise friendly but they are not. The pellets are hard to walk on and get moldy easily (which can lead to eye and respiratory problems).
Humidity levels needed will depend on the species.
Yes it is a Testudo graeca, but all T.graeca fit into any one of a number of subspecies.
Here's a list of weeds and plants you can feed your Greek. http://www.shelledwarriors.co.uk/forum/showthread.php?t=31723&page=3
What are the temperatures in your enclosure, under hotspot, warm end, cool end and night time?
Aaron, I keep all my (indoor) greek tortoises on cypress mulch. Depends on where you live as to how easy it is to find and the cost, but it is worth the effort to get it.
Cypress mulch is great, like CGKeith said. It can be hard to find in some places. I use a combination of aspen shavings and coconut coir, which you could alternatively try. Make sure the aspen is not treated, it'll usually say something like all natural kiln dried. Coconut coir is sold under a few names - ecoearth, bedabeast. If you go this route I highly recommend ordering from a pet supply store online as opposed to a Pet Smart, etc. as you will pay far less for it. This is true for most tortoise supplies. I like Pet Mountain, personally. Carolina Pet Supply is another one I've heard good things about, though I haven't used them myself.