Money is just a tool to represent value. Value is not a zero-sum game. If a person creates something of value, she is creating something that did not exist before.
For that item to have quantifiable value to others though, they must be willing to exchange their money for the new item. The money that is to be exchanged already existed and is supposed to be limited in supply via fiscal policy. If the majority of that supply is owned by a small group of people the value that can be exchanged for the newly created item is limited as well unless those with the wealth want it.
Assuming that the monetary supply is fixed, then there is a deflationary effect. Even those with less money are able to purchase more value as more value is created. This is why incentives for creating value are important to an economy as opposed to just increasing the monetary supply.
Its not free. You are the product. Advertisers pay google and google is then able to provide the infrastructure to provide your entertainment. Its provided to you in hopes that you will buy something based on the ads you are shown. It must also be effective advertising if people continue to pay for it.
There is only so much land, food, and materials to go around.
True(ish). False. False.
I say "ish" for the first one because hopefully humanity will grow beyond Earth in the near future.
Generally, all of the above are false unless you are talking about a population which never stops growing, and in that case that would be the problem. Not wealth inequality.
If you have a population that did stop growing, but in which class divisions exist, and the upper class keeps taking larger and larger share of overall wealth generated by the society, you're going to have a similar problem.