How can I see what my immunity level is without having a tile next to a gate, city, capital or world..

Unfortunately there isn't an easy way. You can go to each of your virus research buildings and tap on it to view its own immunity level. Adding up all 4 (if you have 4) will give you an idea but your specialities and possibly alliance buffs may add on top of this.

You can tap on any plot in New Eden and tap 'View' to see the plot details and your total immunity value. But this is almost the same as you mentioned.