For the second part I vote "no". Malleability covers all aspects of deformation. It is possible to bend some alloys with minimal deformation, but this is unrelated to how the same alloy would deform upon sudden hard impact. I've tested a lot of cast hollowpoints in my days, and even though I was able to mix alloys to nearly identical air cooled hardness, cast them in the same moulds, fired with the same loads, in the same guns on the same day, results would vary. And there was no rhyme or reason to the results. The results were pretty consistent by alloy lot, but different alloys always seemed to perform noticeably different. At that point I switched away from salvaged components to foundry mixed alloys from virgin elements and got much greater consistency and performance.
The design of the bullet also has a huge bearing on expansion, literally everything matters when relying on bullet expansion. Velocity, environmental conditions, distance to the target (a biggie). Everything.
All you can do is test and retest. That's why I don't mix for hollowpoints, and am a bit soured on the idea of relying on cast bullet expansion.