SOP grammar mistake and use of and/or

[ale98]

I have applied to multiple Ivy league schools and was reviewing my SoPs after I sent them. I recently learnt that the use of and/or is very frowned upon. I have used it on occasion in the most important paragraph - which specific areas of study I am applying for. Also in a single SoP, in THE SAME paragraph, I have made the most stupid omission - rather than say "with application to" I have written "with application". How egregious do you suppose these mistakes are? 

[filmic]

A university that rejects you for a grammatical mistake like that is not worth your time