I am creating a spring of variable pitch with closed ends. The variable pitch function has not been working well, so I decided to create three helices and connect them. The first and second helix have the same start angle so have no problem connecting with "composite curve," but the second helix has 12.849 coils and so ends at a different angle than it starts. I have attempted using the angle 305.64deg but it appears that 0.849 coils does not translate directly to 84.9% of 360deg. The closest I have gotten by approximating the angle is between 143 and 145deg, but even then it appears there will be a slight vertical gap. I stacked the helices by creating planes that referenced the endpoint of each helix and the top plane. Is there an error in how I've tried to match the start angle or is it something with how I'm building the reference geometry/sketches?

Create a plane at the end point of the spiral. Perpendicular to spiral.

Never ever calculate angle by hand. You can't get enough decimal to get tit "correct".