I am unable to disconnect the outer tie rod end on my 91 Buick

We used to use a Fork like tool meant for this that you drive with a hammer, Today I saw one that was more like a puller. Should cost less than $20? It does take force.

It's best to use a puller, not a "pickle fork." Using a puller will prevent you from damaging the grease boot.

First, if you're replacing the tie rod end, loosen the jam nut that lock's the treaded portion of the inner tie rod, and with upward leverage (pry bar) applied to the tie rods, a judicious hammer strike, with an appropriate persuader (hammer) to the area of the steering knuckle where the outer tie rod attaches usually pops that tie rod free. I've done it that way for decades.

If you're not replacing the tie rod end, but a different component, don't break that jam nut free.

I also like to measure from the center of the Ball joint to a point maybe 4 inches down the rod, then unscrew, then when New one is xcrewed in you can get it close enough for Wheel Alignment.