full range signal to subwoofer

I can't imagine how, unless you wired a speaker level signal into the low level inputs.

Regardless, with your sub's crossover set to some useful level such as <80hz, you won't even notice that your sub line is full range.

Describe more as to how you hooked it up 'wrong'.....If you hooked the amplifier outputs to the line-level inputs (hard to do) that would be a problem. BUT if you mean you hooked a line-level output from your preamp to the line input on the subwoofer - thats what you are supposed to do, as the subwoofer has a low-pass filter (or adjustable crossover) built in.

A sub should already handles by far the most power. Sending it the upper octaves shouldn't have hurt it at all. If it seems to be working ok then it is, don't worry about it. I've accidentally sent DC to my mains and sub a few times and never hurt a thing. This through a 600wpc at 4 ohms amp.