<p>I don't want this to be a specific producer question, but I would like to know if the Sparkmaker is good enough to print small details in OO/HO scale objects.
I'm referring here to objects like furniture, and other house appliances at scale.
I wasn't able to find any visuals with very small objects for this printer.</p>

Can you tell by looking at the de-adhesion what isn't sticking?
It may be that printing the ASA at higher temperature is melting the BVOH enough that it doesn't stick, being molten.  If so, then it may be possible to print the first layer of ASA at a cooler temperature, slower if necessary to still succeed at extrusion, with fans blowing.  Then, print the next layer of ASA at a higher temperature, also with fans flowing.
A test might be to print the BVOH, then a layer of ASA, and stop.  Let it cool and test the adhesion.  If it sticks under these conditions, then a better command of the temperature profile may offer a way forward.