I think [name_m]Einar[/name_m] is a lovely choice! I love the meaning and the Old Norse roots. I’m not sure it works best as a middle for [name_m]Leo[/name_m], because [name_m]Leo[/name_m] [name_m]Einar[/name_m] is a lot of vowels back to back. Perhaps [name_m]Leopold[/name_m] [name_m]Einar[/name_m] nn [name_m]Leo[/name_m]?
I live in [name_u]North[/name_u] [name_u]America[/name_u] and am a monolingual English speaker, so when I see the name [name_m]Einar[/name_m] my brain pronounces it like “Eee-ner” which does not have a very nice ring to it [name_f]IMO[/name_f]. However, this is obviously the “wrong” way to pronounce it so that just shows my ignorance!
The way you pronounce it (like eyenar), on the other hand, is quite lovely. It reminds me of [name_m]Iver[/name_m] which is a name I’m fond of. It would just take me personally some practice to learn to pronounce it that way.
I think it depends on where you live and how much you care about potential pronunciation issues.