IF formula help on calculating a score

Hi everyone,

I need some help on a particular column on L (see attached test excel file).

I've managed to get this far doing this but still need help on the last step.

I'm trying to create a sheet of questions and using a tick box method to calculate whether they passed the question or not, which will give a score. however if the question if not applicable, i would tick the N/A box as shown in the document however this shouldn't penalize the score the overall score.

for example, if theres 5 questions and only 4 of them apply which they all pass except 1 question that is non-applicable, the total score should still be 100% but as to rather 80%. can someone take a look at what exactly i did wrong or what is missing?

is it my formula for the total SUM wrong? or the IF? this is what i'm unsure of..

i hope someone can help me with this, thanks.

thanks.