Something incorrect about the 917 number you give. Sears Direct site returns 0 results for that number.

model: 917.289341 22hp Kohler 42" deck
model under seat says: 917.289344? Go figure

Yes, there is a main fuse. I do not know the physical location of the fuse on the tractor but it ought to be visible, or accessible under the dash area with the hood raised. Yes, when you turned the headlights on and fed the shorted circuit some voltage, the fuse popped.
Find and replace the fuse and you will be good to go.

I have a multimeter but not sure what to test or how. The mower was/is disengaged as I had just finished mowing and parked it in the drive to cool down before moving it indoors. That is when I noticed the slight smoke which was caused by the loose headlight wire harness contacting the exhaust pipe. I made the mistake of turning on the headlight switch to see if it worked. (Curiosity killed the cat) That is when the fuse made the "snap" sound. The rest is history. I replaced the fuse. Still no action at the starter. I jumped the solenoid poles with a screwdriver which caused the starter to crank the engine but did not start. Also, I looked at the brake interlock (safety switch) but cannot figure out how to remove it. If it must be removed from below, I will have to drop the deck and disassemble brake linkage, etc.
This is turning into a major hassle. Any advice would be appreciated.

Testing Craftsman starter control circuit (with manual PTO for deck engagement).
The circuit testing can be done using the DC voltage scale of a multimeter (herein called VM), or a test light. I will simply state VM and you use whichever test instrument is best for you.
Confirm that your VM (or test light) is functioning properly before you begin testing, a check across the battery posts should suffice.
Testing of some circuits herein requires that the key switch be in the START position when VM probe is touched to the wiring. Because the problem in the wiring might be caused by poor contact of a safety switch or the related wire connectors, be sure that you DO NOT place your hands/feet or tools on or near any parts of the engine that will rotate when the engine is cranking. Testing sometimes reveals the defect when a wire is moved and the engine suddely begins to crank without prior warning.
Testing of wires and connectors is properly done by inserting the probe of the VM into the connector body at the same place the wire enters the connector body. These tests must be done with the wiring connected to the switches for the test to be conclusive. Inserting the VM probe as described will place the probe into contact with the metal wire terminal inside the connector.
Beginning at the ignition key switch, find the RED wire connected to switch terminal "B", check that this wire/terminal has voltage. If NO, recheck the fuse (using VM while fuse is in place, not just a visual inspection). If fuse is good, try to trace the wiring and or harness between the fuse and the key switch for damage/chaffing/break.
If testing RED wire "B" terminal determines there is voltage present, find the WHITE wire connected to switch terminal "S". Position the VM probe to the WHITE wire terminal and turn the key to the START position while observing the VM. If no voltage is present, replace key switch.
If voltage is present on the WHITE wire in this test, move your testing to the clutch/brake pedal safety switch and test as follows: Key switch in START position, clutch/brake pedal down......you should detect voltage on both WHITE wires at the clutch/brake switch.
If you detect voltage at only 1 WHITE wire here when the pedal is down, check that the switch is in its proper place and is adjusted to operate when pedal is down. You can manually operate the switch plunger or lever to mimic the action of the pedal using a finger. If manipulating the switch manually causes voltage to become present on the second wire, see if the switch can be moved/adjusted in the necessary direction to affect proper operation. If no improvement is seen, replace switch.
If you detect voltage on BOTH WHITE wires when first testing the clutch/brake switch, move your testing to the deck engagement safety interlock switch.
With the deck NOT ENGAGED, key switch in START position, test for voltage on both WHITE wires at the deck switch. If voltage is present on 1 wire only, check mounting and adjustment of switch (same as for clutch/brake). If no improvement, replace switch.
If both WHITE wires have voltage when first tested, move your testing to the STARTER SOLENOID. Place VM probe on the WHITE wire terminal of the solenoid and turn key switch to START. If voltage is present, make certain this wire is secured soundly to its terminal on the solenoid and the connection is clean. If no improvement, check that the solenoid is properly mounted (clean secure ground connections) and if a second small BLACK wire is used on the solenoid, this wire is secure and clean both at solenoid and where it fastens to its ground (most configurations have only the small WHITE wire).
If no improvement, use a short length of automotive wire to "jump" from the large battery + post of the solenoid over to the WHITE wire of the solenoid. If the solenoid does not activate, or if it activates without engaging the STARTER, replace the solenoid.

Update: I have determined that all safety interlocks appear to be active (good). I can lock the brake with PTO disengaged, ignition key in "on" position and jump the solenoid poles (screwdriver) to start the mower. I mowed the lawn. (good news) If I needed to dismount, I disengaged the Blade PTO and set the brake. Leaving the seat did not shut off the spark. When it was time to turn off the engine, I did not set the brake and stood up. The engine stopped running. The reverse operation position on the ignition switch works, as well. Not sure where the problems lies as it will not start or turn off with the key.

Well, let's narrow this down to 3 questions.
When you tested the WHITE wire on the key switch per the instructions, did you read voltage when the key is turned to the start position?
When you tested the WHITE wire at the solenoid per the instructions, did you read voltage when the key is turned to the start position?
When you jumper from the BATTERY + post on the solenoid to the WHITE wire post on the solenoid per the instructions, does the solenoid activate and cause the starter to spin?