The idea that burning wood is carbon neutral is flawed because it did not take into account the co2 consumed by trees if they were not burned as fuel and left to continue growing.

The trees are basically fungible in terms of their carbon storage. If new trees are replacing the old ones in the long term there is no effect in terms of CO2.

Second, the Drax powerplant requires 70,000 tons of wood PER DAY. How many trees must be cut down every day to feed this one plant, not to mention a dozen others? You really think it's possible to regrow that many trees every day even in the best managed forest? What about as demand increases?

Well, depending on the type of tree that's probably only about equivalent to the dry mass of 10 to 20 trees per day, which isn't that significant. But also you have to consider that wood pellets are also produced as a waste product from lumber production, so it's not necessarily the case that it comes from individual whole trees. Obviously there's a limit to how much wood you can sustainably harvest in the long term, because there's a limited about of land devoted to tree production and a limit to how much solar energy falls on that land.

Third, using corn for biofuel has caused the price of corn for food to go up, with the biggest impact on the poor. What will this do to the cost of wood for homes and furniture?

That's certainly something to pay attention to if we begin to use a significant proportion of virgin lumber for energy production. It doesn't change the fact it's a renewable resource, it's just a limited resource like everything else.