Your map will be more than adequate to sustain a fortress. To put it in perspective, you could sustain a fortress in a desert with absolutely no trees or water. All the rest are just "luxuries".
Trees will let you make beds, and make charcoal
Magma will help you with smelting, give you obsidian, and give you some fun (especially since it refills)
The lack of a river isn't really a big deal, but if the map is hot enough those pools could dry up. Dwarves only require water to treat their ill, since normally they just drink alcohol which magically doesn't require water. Most of the uses for a river are "just for fun", ie making huge elaborate and needlessly complicated traps, making unlimited magma (by combining it with obsidian), fishing, etc, etc. If you have an aquifer you have an unlimited water source mind you.
The other two things which are nice to have which you don't (or at least didn't mention) are sand and flux. Sand is a completely optional, but you may hit very slight problems later if a noble requests something made of glass (but similarly they could request some stupidly rare item and you'd be in pain anyway).
Flux is useful for making steel, which is much sexier than regular iron (although it doesn't really do that much more).
Regarding the trade depot, you're misunderstanding how Shift-D works. Shift-D lets you see the paths wagons (guys can come on foot easily anyway) can take to your trade depot. If the whole map is red Xs, you need to clear a route. Wagons require a 3x3 space, so if your depot is indoors you'll need to widen your fortress entrance. The other easy things that may block the route are small annoying stones, which you can just build a road on top of and they'll disappear, or a river (which you don't have, brook is okay though) which you'll need to cross with a bridge (also must be 3 squares wide).
Anyway, sounds like you have a perfectly adequate place to start your fortress. Have fun!
edit: noooo, quadruple ninjaed