Keep my garage moisture free

I believe that foam insulation, while great R-value, can be hazardous. It is very flammable, and when it burns gives off very toxic fumes. One example is that nightclub/live music venue fire in RI(?), where Great White were playing, and somebody had a brilliant idea for pyrotechnics special effects. It flashed over in a minute, and fully involved the entire structure in a couple more minutes. 100 people died. Google "great white fire".
Some of the hazards can be mitigated with furring out walls and covering with sheetrock(pref. 5/8").
I like the idea of vents, big ceiling fans for air movement, dehumidifier or A/C, sealing slab, post construction.
Pre construction, you could have installed insulating foam panels beneath the concrete slab, and/or as some suggested simple plastic sheeting.