Ooooooooooooh my... If you can't get through single player, you are total fodder in multi
If you want the easiest route the SP (mayhap you're attempting to do the stratos campaign on your first try? Would explain your difficulties...) then start a new game and just pick James for each mission. When you have the opportunity, don't kill Sirocco - let her live and go after the Ragman. Then, for all the other missions, you will have the queen of all dragons at your side. She can bring your units back to life with a breath, and has a fierce and deadly set of teeth and claws that can strike down most foes in one slash.
As for your graphics problems - try disabling triangle strips in the graphics options menu. Failing that, update your drivers and update DirectX. I had terrible graphics problems with my Voodoo 3 3000, until I changed my driver to 1.05. No troubles then except for the fogging. I'm now using the most recent driver (1.06 I think maybe 1.07 or something...) and DirectX 8.0 and I have no problems at all - the fogging works fine, all the graphics are where they should be, and I'm getting better performance (running in higher screen resolution and detail now with just about exactly the same framerate)