I installed 2-inch Styrofoam insulation in all three of my single doors in 1997 (doors installed in 1988). The garage went from baking oven temperature to something close to ambient. Adding attic and wall insulation and an air conditioner a few years later turned the garage into livable space. We had some 40-degree (F) nights this week and the garage, with no heat, stayed above 70. Nothing compared to your latitude but 30-degrees probably means above freezing in your garage -- "sweater" weather.
Adding the foam to my doors didn't affect the springs at all but the doors did not meet Florida's new building codes (set after hurricane Andrew in 1992). After spending $25,000 to repair and upgrade the roof and buy steel storm panels for all the windows and doors, my windstorm insurance would decrease by more than $1,000 a year except for the flimsy garage doors. I replaced the three doors in 2001 and they each came with 7 steel cross-braces and two more vertical braces in each panel. Rather than buy more Styrofoam, I removed and cut up the pieces from the old doors. Thus the patchwork of foam in my doors.
I can't really hide the braces but seeing your door makes me think about replacing the insulation and painting the cross-braces white. Still not pretty but less ugly,
I am certain the added weight of the insulation has no effect on the springs and shouldn't even require adjusting the opener. If you want to double-check, disconnect the door from the opener track and lower it half-way. If the door slams shut, have the tension adjusted. If it stays half-way, you are good to go.