Well, something must be horribly wrong with your CAD setup because I ran that code which made a 90degree angled leader after asking for 2 points, then I simply changed that l_ang variable to 45 and it worked fine.
You mentioned you tried to do "setq l_45 90" and it didn't work. If that's what you're talking about, that's because you didn't change the l_ang variable, you created a new variable called l_45 with the value of 90.
(setq l_ang 90) in the original code should be replaced with (setq l_ang 45) if you want to change the l_ang variable.