before you buy chains, make sure they are legal where you live, also, can you live with driving everywhere in third gear? Check your tire pressure, and maybe look into having some soft winter (X-ice or similar) tires for the back at least during the winter. But you would probably want fronts too. Getting some weight in the back will help, a couple of concrete pavers might be easier to tie down, but I think sand bags are your best option, and just consider it an annual expense. a temporary solution is to just shovel your truck bed full of snow. Not ideal, and not for long term, but to get you out of a jam, it's been done before.
If you are having trouble driving your truck in slippery conditions, 4 wheel drive won't save you. I've driven many different trucks in some very nasty conditions, and almost all the times I needed to go into 4wd on ice was to get low range, so I could crawl it around. When I lived in Calgary, most of the large pickup trucks I saw wreaked was almost certainly due to the driver being in 4wd, getting going faster than was safe, and finding out that 4wd doesn't make the breaks better. Or as in one case I watched a truck in 4wd walk itself corner-ways into a concrete divider rail because the driver didn't understand that he was no longer in control.
The joys of driving a light pickup truck. My dad owned a 6.2 diesel chevy that was amazingly light in the rear end. should have named that one skippy.