Even though it is after the fact, consider filing a police report with whatever LE agency has jurisdiction at IAD. I'm not sure if you can do that remotely. Take photos of the damage to your laptop ASAP, before commencing any repairs or diagnostics.

Followup on the damage claim with TSA after a few weeks (maybe a month or two?) if/when you haven't heard anything. Be polite but angry. Imply or state that your attorney is getting involved and mention the police report.

As for the laptop, if it is older and/or out of warranty, it may not be worth replacing the LCD, certainly not at the cost the OEM will charge you for a new LCD. Depending on your comfort level dealing with fixing electronics, consider checking out alternate sources (i.e., ebay, web vendors) looking for a replacement LCD and either replacing it yourself (30 minutes with screwdriver and laptop tech manual) or having a local, non-brand-affiliated computer repair shop, do the replacement. There is rarely a reason to spend $500-$1000 to replace the LCD on a laptop when a new model can be purchased for $800-$1200. Also, connect the thing to an external monitor and make sure the rest of it still works before investing in fixing the LCD--the LCD may be the only visible damage but not the only damage.

Edit: One more thing--consider asking (telling?) the LE at IAD or TSA to preserve the video from the checkpoint. If the video shows the screener being as negligent as you describe, you might be able to push and get the screener fired. I don't know about you, but if it were me, getting the screener-at-fault fired and held accountable would provide tremendous personal satisfaction.