Good luck in receiving an adult conversation about ethical or legal issues. I've tried and failed.
As to #1, stealing/theft/larceny is the taking of someone else’s property without consent and with the intent to permanently deprive the owner of that property. In this situation, there is clearly a taking of property. However, every other element of this offense is arguable but not really that solid. I think I would be able to get you off if you were charged. The property can be argued to have been abandoned, so (a) it was no longer someone else's property, and (b) the original owner's abandonment is evidence of their consent that someone else could take the property. In most cases I can imagine, you could at least introduce doubt that your intent was to take it to another location such as the parks dept to find the true owner and ultimately give it back, so (c) there was no intent to permanently keep the property.
I guess the bottom line is that I don't think there's a legal issue here. Better to focus on the ethics of the question.