Post Heller and Bruen AWB's are no-go's but that didn't stop these states from passing them anyway.

You misunderstand Heller, and there's a colorable argument about Bruen. Heller merely held that a state can't prohibit gun ownership altogether - there exists a 2A individual right to own a gun. It said nothing about whether a subset of guns can be prohibited or not. Bruen said that restrictions have to be consistent with the nation's historical tradition of firearm regulation. It's pretty easy to see how if you hit the right judge, you might find one that will rule (at least initially) that there's an argument that AWB's are consistent with historical firearm regulation, since firearms with the characteristics of modern assault weapons didn't exist back in the day and there have existed over the years limits on some types of classes of firearms. SCOTUS might want to roll back restrictions on concealed carry, but they might not be open to letting people manufacture/own brand-new fully automatic weapons.

They're not holding anybody: Biden is paroling these guys right on into the US.

A simple exec order mandating that a blood test is require for all asylum seekers before they may be paroled into the US would do the trick.

Your own quote says that's not true - they're holding about 15% or so of them, give or take. If you show up at the border with no ID at all, you've got a pretty good likelihood of ending up in that 15% who's detained for further investigation. Which is why it's, again, one of the dumbest moves ever for someone who is actually involved in terrorist activity to try to get into the country this way.

As for the blood test - do what trick? What are you screening for? And how are you going to administer, and pay for, bloodwork and labs for that many people?