Is this Mosaic?

[Hking]

New symptoms have appeared, including variegation, a mysterious jelly-like sap, and white fungal-like masses. These symptoms are found on both the trunk and leaves.
The sap has a rubbery feel, like a contact lens. The white fungal-like masses are not like scale insects, but rather like calluses. When touched with a toothpick, the white masses are hard, but the sap can be easily removed, like a contact lens.
It is not clear whether the leaf variegation is a separate symptom from these other symptoms, or whether it is the same. However, the two symptoms are occurring simultaneously.

 

[Wires_Guy_wires]

It's not a mosaic virus.
Sap can leak from wounds, it's what ficus do and what they are known for.
The insects could be scale.

I think you need more plants to be honest, because I feel like you're over-analyzing what's going on and you keep finding the most far fetched answers to very simple things. I don't mean this in a bad way, but the overall look of your plant is healthy and I know the "first time gardener" mental state: it will stress you out and that stress is bad for you. If you have more plants, it's easier to worry a little less

 

[Shibui]

I only see one leaf with yellowing and it appears to be the oldest leaf on the tree. Even evergreen leaves have a finite lifespan. The tree grows new leaves then the oldest ones turn yellow and drop - entirely natural process. There are other causes of leaf yellowing in ficus but the fact that all other leaves look normal and healthy says there's no real problem here.

Without a much closer look at the tree it is hard to work out exactly what's happening but here's some guesses:
Ficus sap is white latex. It's what natural rubber is made from so no wonder it feels rubbery. Sap can come after pruning or any other injury and is the tree's natural way to protect cuts, much like our bodies heal cuts and scratches with blood clotting.
Maybe the white on leaves has dripped from a cut elsewhere on the tree.
Maybe the white is bird poo? Though I guess your ficus is indoors now?
It is possible that the hard white stuff is just dried sap.

The other healthy leaves say don't worry - yet. Wait and see what happens.