They're roughly 2–3 tablespoons.
Filling a teaspoon to level means you put your media in the spoon up to but not over the edge of the spoon. a heaping teaspoon means you put your media in the spoon til it reaches above the rim of the spoon. 1 heaping teaspoon is thus greater than 1 level teaspoon.
Baked filled pastries are best enjoyed the day they are made and don't refrigerate well. Baked unfilled pastry may be frozen in airtight containers for up to 6 weeks.
The best way to keep a fresh baguette for longer is by freezing it as soon as possible. Let the baguette cool completely, then place it in an airtight freezer bag. Squeeze out the extra air and zip it closed. It is best to cut it into pieces so that it will fit into the bag.
Cook your French toast as usual and allow it to cool. Put a sheet of wax paper in between each slice so they don't stick together, and then wrap the stack tightly in foil. You can also place the stack into a heavy-duty freezer bag instead of the foil. Or both!