Looking for advice on making halva w/ allulose - first attempt came out gummy and taffy-like w/ oil separation
It's really better to work in weight especially when cooking with different types of sugar. Trying to change the fineness of sugar, and the sugar chemistry, and then make up for it with adjusting volumes is prone to failure.

Halva is easy to make but hard to get the right consistency. My last lot ended up too soft/sticky. But it's ill-defined: different cooks and different cultures aim for different textures.

So I'd find a recipe that's described as being the type you're aiming for, make it exactly, and only then start substituting.