1. good but not remarkably so. Reasonable, decent, fair enough.
2. within reasonable bounds of expectation. Not extreme or overboard; understandable and tolerable.
- 그는 축구, 농구 실력이 다 웬만하다 (#1): He has decent athletic abilities in both soccer and basketball.
- 그 친구는 웬만한 일에는 화를 내지 않는다 (#2): He doesn't lose temper on anything short of outrageous.
"괜찮아, 괜찮아. 볼살이 많아서 웬만한 충격 같은 것도 자체 흡수가 가능한 신체로 아빠가 DNA 구조를 해 놨어."
=> Don't worry about a thing. Dad arranged the DNA makeup to give you (a body with) thick fleshy jowls which can absorb a fair amount of shock. (You fell, but your jowls are designed to absorb the shock)