If you know for certain the battery is good, then what you would want to do is unplug the small signal wire on the starter and check for voltage while the key is in the Start position. If there is 12V on the signal wire while in the Start position, then you know the control system is working and your only possible causes would be battery/cables/starter itself. With the battery ruled out you would want to double check your cable connections on both the battery and the starter as well as your ground cable. If the cables are secure and in good shape then you would suspect the starter itself.
If however you do not have 12V at the signal wire on the starter when the key is in the Start position, then there is a control system failure.... which would mean ignition switch, clutch safety switch, or the wiring in between and to the starter.
Given that the problem seemed to occur after the clutch job, I would not suspect an issue with the safety switch or the ignition switch and more likely the starter has decided to fail or something went wrong with the wiring during reassembly (loose connection, pinched wires, etc).
WIth regard to the low idle, this is typical behavior on this model and most Asian (Toyota) electronics vehicles in general when power is disconnected as it causes the computer to lose its idle speed adaptations. The problem can be immediately resolved by cleaning the throttle body or less efficiently if the vehicle is allowed to idle untouched for an extended period (15 minutes+) it will begin re-adapting and will eventually clear up on its own after that.