What are some resources I could use to verify statistics that you are using in your presentations?
You are quite right to question raw aggregate data. Fortunately, others have also raised such questions and thus both government and other data gatherers and data processors have generated the inflation-adjusted and per-capita or per-enterprise data you are interested in. The BEA at the Department of Commerce and the BLS at the department of Labor are huge repositories of such data. Also the Census Bureau's Historical Abstract of the US and the President's Annual Economic Report as well as many publications by the Office of Management and Budget in the White House and the Federal Reserve System will offer much of what you seek. Outside the US government, try such research outfits as Economic Policy Institute, Center on Budget and Policy Priorities and such international sites as the OECD, Eurostats, FAO and the UN generally.
All the above have immense web sites as well as suggestions for further data sources. Even Wikipedia would be a way into the data yoiu would find useful. I certainly make regular use of all of these resources when I do empirical work.