"Žofie takes care of him."
Translation:Stará se o něho Žofie.
While o is usually used with locative, that does not mean that it is always used with locative.
Locative implies a location, and - as you can see - that is not the case here.
Starat se o koho/co 'take care of sb/sth' is used with accusative. You are talking about an object of the verb starat se, so you use accusative.
Definitely not. Prepositions used with verbs in Slavic languages don't "get attached" to verbs, but rather to "objects" they're directing to, except if they are a part of the verb (roz-umět, při-jít,...). So, you gotta keep the "o" in front of "něho". Acceptable word orders I can think of are: O neho se stara Zofie, Zofie se stara o neho, Stara se o neho Zofie. I'm not sure about "Zofie se o neho stara", I'd need a native to confirm if it's OK.
"Zofie se o neho stara" is acceptable :) In Polish it would be the main clause (after a comma should be second part of the sentence) /Sorry for Polish, I don't know how "but" and the subordinate clause work in Czech yet/ : "...., ale jej nie wychodzi." (eng.: but she fails)
Yes, Prepositions "get attached" to objects. Between tham can be the attributive (adjective, pronoun specifying an object).