İncreazinf size of custom Key Signature

Maybe it's better to use Scaling: https://musescore.org/en/handbook/3/page-settings#scaling

Some things don't seem right in the examples you provided.
In one of the examples, the lines of the staff seem to be too wide (or other staff elements are small.).
Can you add short versions of the scores here (in mscz format)?

Örneklerde bazı şeyler yanlış ayarlanmış gibi.
Ekran resimlerinden birinde dizek çizgilerinin arası bana fazla geniş göründü (ya da dizekteki dğer elemanlar küçük).
Örnekteki notaların kısa versiyonlarını içeren "mscz" dosyalarını buraya ekler misin?

To be clear: to make music bigger, do not use the "Line distance" in staff properties, that's for something else entirely (creating notation that is non-standard in others besides just the key signature). To change the size of all staves in your score, you Layout / Page Settings / Staff space (scaling). Or use staff properties to override the Scale for just this staff, if you want others normal size and only this one bigger.