Thanks for the suggestions guys! I guess the dealer may be a good idea here. Although, the other ideas given here are pretty good, and may be worth a shot. The impact I was using was a 1/2 inch electric Ridgid impact, I'll throw a link for it down below. Its crazy, I have been able to remove any other fill bolt I've tried, but this one is something else! And then with the silicone being so close, heat doesn't seem to be an option unfortunately. If I do take it to the dealer this time around, then should I crack the fill bolt off when I get the car back home and do something to make it easier for the next time so I don't have to take it to the dealer again? From my experience, dealers usually torque things down with a few ugga duggas making it difficult next time I try to DIY.
RIDGID 18V OCTANE Brushless Cordless 1/2 in. Impact Wrench (Tool Only) with Belt Clip R86011B - The Home Depot
RIDGID introduces the 18V OCTANE Brushless Cordless 1/2 in. Impact Wrench (Tool-Only) with Belt Clip. OCTANE Tools feature high performance brushless motors and advanced electronics, providing best-in-class