Love these merge threads. They usually come up every year or so.
Illinois rules of the road state: "When entering an expressway, you will usually find a speed-change lane. This lane allows you to gain the speed necessary before merging. Signal and look for an opening in the traffic, match traffic speed and merge with traffic when safe."
Notice there is no statement about "yielding", although "when safe" is kinda the same thing.
Also, the merge sign says "The driver on the expressway slows down to let the driver on the ramp merge."
So absolutely when in Illinois, you should adjust your speed to allow the oncoming vehicle to merge safely.
The propane is stored in the tank in liquid form. It has to change to a gas to make it to your furnace. That takes heat. It is possible that when it is really cold outside, there is not enough heat to evaporate the liquid to a gas fast enough to keep the furnace running.
When I was there in July, the Ranger at the pay booth told us to park in the RV / Trailer parking, unhitch and drive the toad up. He did not make it sound like it was optional.
The RV / Trailer lot was pretty full. Ironically, there would have been room up at the top, had I tried driving the RV up.