To run the 2 mics into Pro Tools, keep one plugged into input 1 of the Mbox, and the other one, plug into one of the first 10 channels on the Behringer. Then, on the back of the Behringer theres direct outputs for each channel, so if your 2nd mic is plugged into channel 1, then run the direct output from channel 1 to the "input 2" line input on the Mbox. Your second mic can then be selected in pro tools by setting the input of an audio channel to "mbox input 2".
In fact, to make things more logical, you could plug both your mics into channels on the Behringer, and use the Line input on both channels of the Mbox, rather than using the mic input on one and the line input on the other. That way both of your Mics will have EQ and routing options before they enter your mbox.
The Axiom 49 is a midi only keyboard, meaning it has no sounds itself, the sound you hear from playing it comes from your computer, so theres no way to plug it into the mixer.
As for hooking the Mbox up to the mixer, the last 4 channels on the Behringer are stereo channels, so you just plug left and right monitor out on the Mbox, into the left and right inputs of one of the stereo channels on the Behringer. Then you'd run the main out of the Behringer to your monitors.
The Mbox has to have the USB cable to your computer though, as this is how it communicates with pro tools.
Hope thats some help, if you get really stuck, drop me a message I'll do a wiring diagram or something for you.