It is stored and transported in a large flat box and us taped all four sides. Inside the box the paper is placed inside a light tight black plastic bag that is over sized and folded at the top.

Yes. Inside the box is another box and the roll of paper is sealed within black (opaque) plastic. I usually keep this particular product in stock in my darkroom. I do have a 54" paper dispensor though. It is made for the photo industry and has a built in cutting blade so it makes it easy for me to use rolls of paper. The rolls allow me to cut sheet sizes that I happen to need since many of the sizes I want are odd. I use the end pieces as test strips. The main issue with using rolls of fiber based paper is the curl that it has after you cut it. The memory of the curl from being stored in a roll makes it difficult to lay flat when you print onto it. I have a variety of Saunders easels and they accommodate magnets to hold the paper flat. I also use tape to hold the edges down prior to place the easel blades over the paper. I still use magnets to hold the blades flat because the curl will actually lift the blades. I use a water bath prior to placing the exposed paper into the developer. This allows for even distribution of the chemicals over the surface of the paper, otherwise the edges curl out of the developer and the print does not get developed evenly. Alternatively, you can use your hands to hold down the exposed print in the developer.

This paper would be 255 gsm

In terms of basis weight, this paper is 255 GSM. However as packaged (8 x 10", 250 sheets) the product is approximately 9.5 lbs.

I have printed many color negatives on variable contrast paper with excellent results, IMO. Will need to add about 30-40 magenta to the filter pack or head to compensate for the yellow/orange cast of the color negative, which will of course increase exposure time to some degree, but easily determined with a new test strip. I have not noticed any degree of loss in sharpness using 4 x5 negatives up to 16x20. D. Webb at WebbPhoto

Yes, but be careful. Cautious testing is indicated.

Ilford Multigrade FB Classic Paper is estimated to be around a 3 to 6 ISO equivalent.

I don't think this question should be addressed to me. B&H would know the answer.