There are only 35 Aurei Cards in the game (not 40 as in the rulebook mentioned).
Based on the description of the Land and Intrigue cards, you are not allowed to play fleets and/or armies in a greater number of Land/Intrigue SYMBOLS.
A word to the “base income”: you collect the base income of 2 Aurei only, if you don’t lay down any card, not every turn!
If I play a Senator (or more) on my turn, I get whatever my income would normally be, and then add 1 to that! The Senator doesn’t limit your income to 1 Aureus.