Learn English – “TV”: is it formal or informal

I don't regard "it has a huge amount of assets" as informal, but I do regard it as bad writing, and would instead say "it has huge assets". Note, besides not regarding it as informal, I also don't regard it as formal, nor would I regard it as formal if a synonym such as major, substantial, significant were substituted. All of those quantities are quite indefinite, and I think a formal statement (in sense of official statement) should give more-precise information about assets or debt.

It is only ever used in a formal medical sense, with examples from the sixteenth century.

Stool derives from the name given to an enclosed chamber, or commode, used for producing stools.

The most usual form is in the plural.

d. A discharge of fæcal matter of a specified colour, consistency, etc.; the matter discharged (chiefly pl.). (OED sense 5d).

It is certainly NOT a slang expression, and I have no idea why it would appear in street dictionaries.