Based on your subject size and camera distance, you need a lens that covers 6 deg (5cm area of interest at 50cm distance) to 54 deg (30cm area of interest at 30 cm camera distance).

On the wide end, you need 22mm for an APS-C sensor to frame your subject horizontally. For a Full Frame camera, you need 35mm. On the long end, you need 210mm to frame your subject horizontally for APS-C, and 340mm on a full frame.

30 cm is fairly close to be taking pictures; minimum focus distance is a real concern for many lenses.

Based on your requirements, I think the 24-70mm f/4L IS USM is the best choice.
- 24mm on the wide end is almost wide enough for your 30cm subject at 30 cm camera distance for your 7D. Hopefully moving the camera back a few inches won't be a problem.
- This lens has 30cm min focus distance, which is important for your application. The 24-105 f/4L IS USM (version 1) has a min focus distance of 45 cm. The 17-55mm has a min focus distance of 35 cm.
- Macro mode. This reduces the min focus distance to 20cm and increases the magnification to 0.7x.
- Full-frame compatible, if you ever get a full-frame camera. It is also a really nice general purpose lens, if you ever want to use it for other things.
- It's an L-series lens. Top-notch quality, durability, etc.
- It is $900 new, vs $830 for the 17-55mm f/2.8.

On to lighting...

Could you use a speedlight with a Rogue FlashBender? You could even get a coiled TTL cord to hand-hold the flash off-camera.