For food security, I prefer to keep a garden of fresh food rather than stockpiling processed "food". But I do store a lot -- we have a deep freeze that is currently FULL of fresh produce from this season, from my own garden and from the farmer's market, as well as some prepared dinners like soups and curries that I made up then froze.
We have a utility room in the basement, where the well pump and water tank are, there's also a built-in tool table and lots of built-in shelves. We use those for storage of whatever can't stay outside in the shed. One whole shelf is dedicated to my canning -- homemade jams, pickles, salsas, ketchup, stewed tomatoes.
I have to say, though, that it never occurred to me to also store 'big' food items down there... like a big bag of rice, or the bag of potatoes that's currently taking up the bottom shelf of the kitchen pantry. I keep lots of large kitchen items (the 10-gallon stock pot for instance) that are only used occasionally down there, so why not big bags of rice or beans? It's brilliant! And will clear up some much-needed space in my kitchen cupboards.
As for finding more room for the OP to store her bulk buys... I'll kind of have to agree that if you have no more room to store food, then you can stop stockpiling. Maybe you want a full year, but maybe that's just not realistic.
Or maybe you can look at what you have and see if there are things that would serve the function better but in a smaller space. Like, if there are lots of crackers. Crackers aren't very nutritionally dense, aren't very filling, and take up a lot of space for little reward. They're nice to have around, but if I were faced with a situation where I had NO income and had to live of whatever I had stored up, I wouldn't be first running to the crackers. Eat the crackers now and replace them with something nutritionally dense.
Same with the Jello. It might be yummy, but it's not very healthy. In a desperate situation, I would reserve our storage space for the most sustaining food in the least space, not 'treats'. Jello is really just flavour and sugar. A great treat, but it's not going to help you survive a year of thrift. Keep a few boxes sure, for the occasional treat, but no need for a stockpile of the stuff.
And at the very least, ditch the boxes of the ones you keep. Put the envelopes straight into a bin, maybe label them with a Sharpie so you know what flavour it is. Probably save 1/3 to 1/2 the space there.
But really, if I were stockpiling for a just in case meager living scenario, I'd focus on buying up nutritious and sustaining food when it's affordable and if there's no room for it, I'd remove something less essential, less healthy, and just eat that now to make room for the better stuff.