Assuming that the "fog" is silver then yes, more first-development. But if the fog is some other layer like anti-halation dyes, then more development obviously won't work; you'll need some way of stripping those dyes. Maybe try hypo-clearing agent, but I know nothing* about these specific films and what chemistry they are expecting! Maybe your colour-development stage is going foggy - you are after all using probably very different chemistry. I would try some E6 reversal bath, CD and bleach instead of the light/RA4/C41 mongrel process you're doing. When you say it went orange, was it transparent-orange (like C41 mask) or opaque-orange?
Contrast of 1.0 just means that the medium has the same brightness range as the scene. Normal negatives are about 0.7 and chromes are usually about 1.2 I think. The contrast-index number is the slope of the density/exposure plot in log-log axes.
Indeed, I would not use Rodinal 1+100. I would suggest a continuous-agitation scheme with a more-concentrated developer, e.g. Rodinal 1+50 (with at least 10mL concentrate per roll). Or any other developer you like as long as you're agitating it enough to avoid heavy compensation effects. Since these are slides you're making you NEED to get the exposure right and you don't want to just flatten out the highlights with compensation. Yes, you will blow extreme highlights unless you accept poor contrast. That's the nature of a reversal system; they clip your dynamic range in both shadows and highlights.
* doing the develop/bleach/colour-redevelop thing implies that we're assuming it's chromogenic reversal film. It may not be that; it could be more like kodachrome (dyes are in the developers) or cibachrome (developer destroys dyes I think). It might not be possible to get anything like an acceptable result using reversal and chromogenic developers (CD-3, CD-4, etc) because of a fundamental incompatibility in how the chemistry of the film is designed.