Welcome to RV.net, I'm sorry to hear about the damage to your RV.
As consumers we have to stay diligent. Used to be windshield washer fluid was all about the same, but not anymore. Most all companies make a summer blend (when Bugs are bad) and a winter blend (when Ice is bad). I think Prestone could make it more clear on the label, but that product is probably only sold in the summers. Other two major manufacturers Rain-x and Peak both put a clear label on the front +32F.
To get it out, you can try to remove the hose on the bottom, which is a pain I'm sure. Or you can use a siphon hose to suck it out. Or you could sit with your finger on the sprayer trigger until it's empty, but I'd at least lift the wiper so they don't rub over the windshield the whole time.
I buy the Bug stuff for my Motorohome and Jeep since both are like a brick wall going down the freeway, they love bugs! Come September I either drain the reservoir or in my Jeep I being mixing in the winter blend.
In the end we have to stay on top of our vehicle maintenance, nobody else will these days.
Happy Camping!