1. The oil supply is not "finite". The earth has a carbon cycle where plate tectonics drive carbon into the mantle where they become hydrocarbons. This is not coming to an end any time soon as far as I am aware. However, past deposits (into the mantle) may have been much greater than what is happening now which means less oil for the future - could be much less.
From _Introduction to Organic Geochemistry_:
The major prolific oil source rocks were deposited during global marine transgressions. As for coals, there appear to have been two main episodes of oil source-rock deposition: one during the Palaeozoic, peaking around the Deconian, and another during the Mesozoic, peaking around the Cretaceous. Such periods were characterized by marine transgressions on to continental margins, crating suitable conditions for the production (e.g. high nutrient supply) and preservation (e.g. anoxic basins) of sedimentary organic matter (Klemme & Ulmishek 1991: Section 3.4.3a). This is reflected in the correlation of phytoplanktonic abundance with organic-rich sediments in Fig. 4.31. The Palaeozoic peak in the phytoplanktonic production can be attributed to the dominant, organic-walled organisms of the era (acritarchs, green algae, and cyanobacteria). The latter productivity peak was characterized by major contributions from, initially, calcareous (cocccolithospores) and, subsequently, siliceous phytoplankton (silicoflagellates and diatoms).
Unless I'm misinterpreting the text the deposition of organic material into the mantle that is the source of nearly all of the oil extracted during this age occurred under conditions very different from today during a period 150 million years ago that lasted for approximately 100 million years. Under the subsequent & current global conditions the contributions to oil reserves are negligible, particularly given our rate of extraction.
2. Our agricultural system is becoming more efficient year-over-year. Production is not directly and exclusively related to hydrocarbon energy input. Genetics and other biotech techniques have boosted production and opened up new areas of the world (arid areas) to production.
While agriculture does not rely exclusively on hydrocarbon energy input, as the solar energy input is essential for the growth of plants, in order to increase yields from available land & sunlight beyond their natural capacity to support an artificially inflated global population we require significant energy investments in the form of fossil fuels. From
Eating Fossil Fuels:
In the 1950s and 1960s, agriculture underwent a drastic transformation commonly referred to as the Green Revolution. The Green Revolution resulted in the industrialization of agriculture. Part of the advance resulted from new hybrid food plants, leading to more productive food crops. Between 1950 and 1984, as the Green Revolution transformed agriculture around the globe, world grain production increased by 250%.4 That is a tremendous increase in the amount of food energy available for human consumption. This additional energy did not come from an increase in incipient sunlight, nor did it result from introducing agriculture to new vistas of land. The energy for the Green Revolution was provided by fossil fuels in the form of fertilizers (natural gas), pesticides (oil), and hydrocarbon fueled irrigation. The Green Revolution increased the energy flow to agriculture by an average of 50 times the energy input of traditional agriculture.5 In the most extreme cases, energy consumption by agriculture has increased 100 fold or more.6
In the United States, 400 gallons of oil equivalents are expended annually to feed each American (as of data provided in 1994).7
...
In a very real sense, we are literally eating fossil fuels. However, due to the laws of thermodynamics, there is not a direct correspondence between energy inflow and outflow in agriculture. Along the way, there is a marked energy loss. Between 1945 and 1994, energy input to agriculture increased 4-fold while crop yields only increased 3-fold.11 Since then, energy input has continued to increase without a corresponding increase in crop yield. We have reached the point of marginal returns. Yet, due to soil degradation, increased demands of pest management and increasing energy costs for irrigation (all of which is examined below), modern agriculture must continue increasing its energy expenditures simply to maintain current crop yields. The Green Revolution is becoming bankrupt.
3. Worker productivity is also increasing, meaning we get more product per energy input. Is it enough to offset potential future drops in fossil fuel supply - probably not - but it helps.
But what is responsible for the increase in worker productivity? I see a couple possibilities. Necessarily, a portion is the conversion of energy from our environment (sustenance) supported by hydrocarbon-fueled agriculture. Also, perhaps, the increasing industrialization, computerization & automation of human activity; which is powered, developed & manufactured by large energy investments provided by fossil fuels.
The number of products derived from oil are staggering. Machines require lubrication, derived from oil. Plastics & the myriad products produced with them, soap, medications, pesticides, fertilizers, ink, tires, personal hygiene products, solvents, &c. are all produced from oil. Due to this it's not just the lack of energy that's concerning, it's the loss of all the products that make the modern condition possible.