Mass deleting and/or selecting only high res pics

[Alexander Chalkidis]

I loved Photos and uploaded all mypics. About seventy thousand of them. Problem is that SOME (don't know which) went up at full res, so my quota is full.

1. Can I somehow find the offending large pics? Tried various types of searches to no avail.
2. How can I mass delete them all (to reupload at normal res)? No, what everyone says doesn't work. Using Shift and selecting first and last pic won't work with this many.

Any ideas? My Gmail account is useless as it is full now. I even deleted all my email (big mistake!) in my desperation...