I suspect that either the variegated or plain Arundo donax will do very poorly under these conditions.

Your first question, "will it survive?"
In my experience, Arundo donax doesn't grow well in pots. If your area is wet from now until late April it will probably undergo a lot of freezing & thawing during & I really don't think Arundo donax will like those conditions either. Actually, if the first doesn't kill it this surely will. Not to mention, Arundo donax 'Variegata' is not nearly as vigorous a plant (or as hardy) as the species.

"2nd, will it fufill the requirements ...." Well... visually pleasing is in the eye of the beholder. Personally, I love the look of this grass. BUT, the general consensis of non-grassy folk is that is looks like a large corn plant on steroids. It won't make a very solid screen as it is very open growing. And assuming it survives your tough conditions, it takes quite a while to get going in the spring, waiting for the air & soil temperatures to warm up.

"3rd how spreading is this plant in zone 6?"
Not very..
Search 'Arundo donax' on this forum & you will be treated to a wonderful discussion of this plant accompanied by lots of pictures.

Two thoughts:
How about planting the area with a shrub that naturally grows in these conditions. Plants along our river undergo seasonal flooding & freezing conditions so I would look in an area like that for inspiration. (Arctic willow, pussy willow, Alnus spp., Highbush cranberry, etc.)
Or
If you are really ambitious you might be able to do an attractive drainage project. Maybe a seasonal river bed (dry riverbed look in the summer) with some raised berms where you could grow a larger range of plants.
good luck!