I think the step from line 4 to line 5 here is almost the dodgiest.
It asserts that the series
-1+1-1+1... = sum((-1)^n)
converges to a sum of 0.
Even a high school kid should know that the alternating series diverges.
In my opinion, worse still is that this Ubaldus guy believes that his false proof of 0 = 1 means that god must exist! If anything, it should only prove that 0 = 1 and mathematics = rubbish.
Wait a minute, couldn't one use the exact same reasoning to prove the non-existance of god? A false statement implies anything. It's like asking what would happen if something impossible happened, it is complete rubbish.