Hi and welcome to the forum! I don't understand what your fourth combinator is for. You can already do this with one combinator. Also, you could use a constant combinator with -2000 coal and -3000 iron and feed it & your storage amount into a decider combinator with the condition "each > 0...

TL;DR I would like to be able to perform "AND" and "OR" operations in one combinator What ? Instead of having to use three decider combinators + an arithmetic combinator and 3 circuit signals to determine if there are, for example more than 2000 coal and 3000 iron in a network, ...