While I understand your frustration with philosophy, the examples you bring up of marx contradicting himself aren't actually contradictory. When marx says that a commodity is a use value, and then latter that it is an exchange value, both are correct.

Commodities are members of both the use value and exchange value sets of items. It is no different from me saying that "camels are animals", then latter on saying that "camels are dessert dwelling creatures".

I think you will get a lot more out of marx if you do actually treat him literally, while being careful in remembering that the meanings of some important words have shifted over time. Marx is one of the few philoaohers who was heavily inspired by contemporary science. If you are familiar with science, and a bit of history, you will actually see a lot of parallels between marxist concepts and scientific/mathematical concepts.

For example, exchange value and labor-power are direct economic analougues of heat and horse-power. The concept of contradictions was taken from derivatives, and his reproduction schemes that he invented in volume 2 of capital are rigorous mathematical treatments of the economy that are still used today, even by bourgeoise statisticians.

Marx was heavily interested in science and maths, frequently attending lectures whenever he could. He always kept up with the latest scientific developments. He would often even do things like writing letters to people like Charles Darwin asking them for clarifications on their theories.