If the alum hubs or caster blocks are tapped to a 3mm thread, use the 'fixing balls' (has the hole in the center of it) on the outer end of the turnbuckle ballcup. You may also need a longer M3 screw, something about 20mm long or a bit longer I think. I prefer to sue cap head screws for this application, the head strips out less easily when torquing the screws down. Use steel screws, stainless is weaker than steel screws. You have the option to tap the hole to 4mm thread and to use the optional steel 4mm thread ball stud for more strength. The 3mm screw setup you can bend or break screws in hard crashes. The 3mm screws also bend/break a lot easier if you don't thread lock them and/or check them preventing them from backing out.
Bound up steering, can't help you with that. Either some part(s) are defective or not installed properly. I've never had my spindles bound up. You have the caster block, kingpin bushings, 4mm kingpin screws, and spindles. Check to see if your axles are rubbing anything. If using Tekno axles this might be the problem.