My course loads slowly for users. Apparently the "Aptiva" SWF file (which is about 100MB) is taking a long time. How can I reduce that file size or optimize to get maximum load speed?

At 100 megabytes I'm not surprised it loads slowly.

You need to split your course up into a number of modules.  I would suggest 5-10 would be good.  Aim to have each module no more than 10 megabytes.  You can package the modules together for the LMS using the Multi-SCORM Packager tool that comes with Captivate.

Also, check your preloader percentage setting.  It may be set to the default of 100%. You can try reducing it to 25% and see if you get any 'buffering' reported back by test users.