Its hard to say if the soil will be safe or not, however, since it was most likely heat cured-Personally, I would use it...but that is me and I sometimes will take chances. If you can, I would also go and dig some fresh dirt and mix with it-sift the two together to get any larger pieces of debris out.
If you will be adding any large hard scape items-I would place them in after your first inch of soil/dirt-especially since you would need at least 3in of dirt/soil in a 100gal tank. This will help prevent anaerobic spot due to compaction/weight of the large hard scape item. Also, be sure and place the heater, filter and tall hard scape items in the tank-then place your top to make sure everything fits right...Kinda a dry run so-to-speak....I didn't do this once and had to tear everything down and start over....lol....what a mess....lol....