Dispel Magic has unusually flexible targeting parameters, so it actually depends on how the spell is cast. If the Dispel Magic spell is cast targeting you specifically then you're immune to it, but if the caster specifically names the spell they wish to dispel they can target the spell directly, in which case you're not the target and your immunity doesn't come into play. Disjunction always targets spell effects and items, rather than creatures, so the fact that you're immune does nothing to prevent it from targeting and neutralizing any and all spell effects affecting you.
It is still not likely to affect Spells like dispell Magic because they technically do not affect the character, but how about something like Deeper Darkness?
This doesn't change anything with regards to Dispel Magic; you're still immune to Dispel Magic, but your spells aren't immune, and if the caster targets your spells directly and not you then your immunity won't protect your spells.
Similarly, this immunity does nothing to help you against Deeper Darkness. The spell does not target you or directly affect you. It affects the lighting level around you. The fact that you cannot see in supernatural darkness is immaterial to your immunity; the spell just isn't affecting you.