I'll deal with each issue separately. Install a security system. Door and motion detectors. They also know your buildings weak points for forcible entry. Buy a serious safe, with a drop slot for periodic cash drops.
Floor safes are the best.
They are impossible to force open or carry off. Robbery Protection, The decal and the safe statement usually discourages would be robbers. Video Surveillance Camera System, either real or dummy is quite a deterrent. Don't keep visible large amounts of cash in cash register drawers. Drop all large bills on the hour.