The fix I put in should be in the build your using, and it does work in my testing. It should be stripping all trailing spaces, even beyond the truncation line. To confirm, you are using is "Strip all trailing spaces", in the SlickEdit Preferences > Languages > IBM HLASM > File Options > Save Options > Strip trailing spaces. Is this correct?
For the IBM HLASM hang, I have a hotfix specifically for Window 32-bit build. I am attaching a hotfix that should address that. You will need to bring up the SlickEdit command-line (bound to ESC in most emulations) and use the load-hotfix command. You will be prompted for a zip file, point it to the attached zip file which you will need to download. Then restart Eclipse. Should be fixed. If you need a 64-bit Windows version, I can provide one of those as well.