ok I can truly understand your frustation there because no one wants to spend on something that you're not certainly sure whether if this going to resolve your issue. Honestly for your disa valve, it appears to be great looking to reuse; but the (red gasket part maybe slightly out of range). And this is mostly the part that actually blocked the compression from coming out on the disa valve. And sometime the leak could be so small, anywhere but you can't even see it N'less perform a smoke test on the car.
I wouldn't require you to buy a new disa valve neither, as vacuum leak may have caused by different other locations. But once again: Disa valve failure, cracked in the elbow, intake manifold gasket, Oil separator hoses, mass airflow sensor are the most common cause for a vacuum leak on these cars. For this reason, I recommend you just like I did to perform a smoke test where you can see right-away whether if you have a vacuum leak or not, and where exactly the smoke is coming from.