-extruder starts extruding prior to starting the print and must be wiped before starting print
This can be an issue on any FDM printer as the plastic already in the hotend heats up and extrudes out of the nozzle. This is called oozing. To help, I make sure to retract a little bit before starting a print to reduce the amount of oozing. I always use a skirt (prints lines around the main part) to prime the nozzle before it starts on the main part.
-issues getting the plastic to adhere to the aluminum base
I have a glass bed so not sure what I can recommend for aluminum, but I would recommend googling around and seeing what others do, I think tape is a popular choice.
-plastic extruded thickness is variable and super thin
You said that everything is level, but you might have the nozzle too close to the bed. Try backing it off a little and see what happens.