The shift lock override has nothing to do with the other problems. The 850 has a micro switch under the console next to the shifter that might be bad. There is also a cable from there to the back of ignition lock which can get stuck - a drop of oil helps that.
Listen for a 'click' when you push on the brake pedal when in park - engine off and key in pos II.
Do your brake lights work?

As to the other problems, check the turn signal fuse to see if it is loose.

And after starting the car, wiggle the ignition switch to see if the lights come on. If they do, you need a new electric portion of the ignition switch.

Klaus
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Why are Volvos so endearing? Its just a car.