Looking for advice on making halva w/ allulose - first attempt came out gummy and taffy-like w/ oil separation I'm trying to create halva, and my first attempt ended up with something that wasn't crumbly like halva is supposed to be - instead, it ended up a hard, taffy-like confection that was tasted like halva but had none of the correct texture. I also had oil separation - when drying, the end product sweated out a lot of the tahini oil, so the end result was more dense than I wanted. Looking for advice/pointers on what I can do next time.

Note: I'm using a different sugar called allulose that very similar characteristics to regular sugar (sucrose). http://allulose.org/reformulating-products-allulose-considerations-flavor-profile-freezing-stability-sweetener-compatibility/

The (seemingly very simple) recipe I tried to follow from https://www.youtube.com/watch?v=64_ckmBf01M:

Ingredients:


2 cups of granulated sugar (the recipe calls for granulated sugar, and allulose I bought was in powdered form, so I actually used 1 1/8 cups powdered allulose for equivalency)
1.5 cups of tahini
1 tsp vanilla extract  
0.5 cups of water


What I did: 


Heated water, allulose to 160 degrees F.
Warmed up the tahini. It was supposed to be heated up to 110 degrees, but I accidentally let it go to 150 F. Added Vanilla extract to tahini. 
Turned off heat. 
Slowly mixed warmed tahini into sugar (well, allulose) solution.
Transferred the whole concoction into pan for cooling.  


Everything looked good while I was doing the cooking, but as I mentioned above, the end result was more like taffy than crumbly, which is what I expect halva to taste like. The fact that the thing I ended up with released (sweated?) a bunch of oil was also off-putting. The taste wasn't offensive and the result of my experiment is perfectly edible. Just not halva.

I know that I overheated the tahini a bit, but I didn't think that should have mattered. Or was this my mistake? Maybe I should add more tahini or more sugar? Or is there a specific timespan to mix the two together? Why did the mixture release all the oil instead of setting correctly?

Thanks in advance for any advice you can offer. 

Thanks,
Greg
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.