Estimate capacitor parameters
Capacitance is given by:



This is the formula applicable for free space or vacuum. If you are using a dielectric material between the plates, you multiply the resultant capacitance with the relative permittivity of the dielectric material. For poly-ethylene, relative permitivitty is 2.25.

For simplicity, lets start with flat sheets of aluminium separated by a polyethylene film:

Assuming polyethylene thickness = 15 microns
And dimensions to be 20 cm x 50 cm

Your capacitance will be C = 2.25*8.85418782 × 10^-12*0.2*0.5/0.000015 F = 0.133 uF

Now, if you intend to roll the flat sheets on a bobbin, things will change. Consider the image below:



Now, all of a sudden, both sides of aluminium foil start acting as capacitors. Black is one plate and blue is another plate of aluminium. White space is dielectric.

This should approximately double the capacitance.

Now coming to your questions, break down voltage appears to be very different across different sources:



Capacitance calculated above.

Ideally there should be infinite current at zero resistance discharge.