The thread end of the screw should have been swaged (smashed flat or have an X pattern) to prevent the screw from coming out. As Dan suggested, if this is not ground off before removal the screw can damage the threads in the shaft making it difficult to retain the screw even with loctite. Steel shafts usually survive but brass shafts can actually break where the screw passes through. I always use a new screw for reassembly and prefer green wicking Loctite rather than red. Green is applied to the threads after assembly and in very sparse amounts!
I leave all springs and detents in place on my Walbro or Walbro clone carbs. I don't see any reason to modify or remove anything. I add longer arms when necessary as shown in my photos above which gives plenty of leverage to overcome most resistance. On the first photo I posted, the arm was in interference fit to the firewall so I relieved the firewall for clearance. You do what you have to do to make things work.