Wheel Chocks, slideout questions

[katina]

I am new to this - have a Springdale 311RE. As I type I'm having a concrete pad poured at my spot. When I move it back, should I put wheel chocks by the tires and how many do I need?
And -
I have 2 slideouts - opposing. If I decide to leave this here (Michigan) for the winter, ( yes it will be winterized ) but can I put my slideouts in/ out if I come up here for a day or two - obviously not when it's 20 below.

And - as long as I'm typing, does anyone know how much weight the slideouts can hold? My friends aren't big, but curious if two 200 lb adults can sit on the couch - for example.

Thanks!!