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