Simple line problem

[ColdH2Odvr]

I'm guessing there's a simple answer but I haven't found it yet so... The problem I'm having is that the endpoint handle of a line isn't actually at the end of the line, it's offset by half a line width. If I set up guides and snap the end of two lines to the intersection, the result is not a smooth transition but a step. I can tweak the points but changing the linewidth requires more tweaking. Any suggestions on the best way to deal with this? Also, is there any way to get the end of line handle to correspond to the point of the arrow when using arrow line ends? Thanks in advance for your help!