Not a locksmith, but I've worked in a bank and I'm pretty familiar with how these things work.

First of all, safecracking can only succeed if the safe is in working order. Drilling that cylinder was a mistake. It would have been a very easy cylinder to pick, but that opportunity is gone. The problem is that good safes have mechanisms to defend against exactly what you did. For example, some have a piece of glass or a spring surrounding the lock. This is an anti-tampering mechanism, which supports a deadbolt. If you remove the lock by force, the spring springs or glass shatters and a deadbolt drops into place, making it impossible to unlock the door. It may be that some similar mechanism is in place here. The reason I say this is that simply turning that slot with a screwdriver should be enough to unbolt the door at this point, yet you are having no luck.

Lock bolts are generally case hardened steel, and the more expensive the safe, the more bolts there will be. So even if you could figure out where they were, you'll find they aren't easily cut. On a big safe, bolts typically engage on more than one side, which means the door will hold even if the hinge is cut. When the timers on a bank vault fail, the entry mechanism is an acetylene torch.