The front brake sensor "modification" is fairly common and nothing to worry about. That top section of vaults scares me a little but as Mountaineer84 says, they could all be the result of the weak battery that was noted by the mechanic. In a perfect world, you would get a new battery installed, the vaults cleared and see if they come back. Those airbag vaults can sometimes be a bear to track down if it isn't battery related. Maybe the seller can borrow a battery for the test (or you can work out a deal to buy the battery for him/her if the car checks out after)?