Is it unsafe to use a torch to heat up a seized bolt in hopes of loosening it if it is bolted to the strut on your car and the strut says gas pressurized?

The safe course here is not to use heat. I describe half a dozen heat free solutions in my book the first four are:

1) Clean up the bolt and the areas around it to allow lubrication to penetrate.

2) Liberally apply a penetrating lubricant and use brushes to work it in and further clean things.

3) Try to rock the bolt from side to side, adding more lubricant.

4) If none of this helps try a freeze and release lubricant... much safer than heat in this situation.