No offense, but if it was my car,the next step would be to test for voltage at the solenoid wire (the little wire) when the key is turned to Start.
And here's another not so common possibility - the mechanical pieces of my ignition switch got so worn that they would not turn the electrical portion of the actual switch. I had to take the switch assembly off the column, open it up, and bend the flat rod that transfers the twist from the key to the switch, to give a little more twist when I turned the key. If you've never had one apart you'll figure it out when you do.