Good logic. Your weakness is the following sentence
a dependent clause has a Subject and a Verb but It conveys only a partial meaning or in other words, it is dependent on another independent clause to convey complete meaning.
This isn't true because of the vagueness of the phrase 'partial meaning'. Since all words in a sentence contribute to meaning, the meaning of sentence will be partial whatever words we leave out. Take this sentence: "The apple, which was red, was on the table." You probably correctly identify 'which was red' as a dependent clause, but note that it's still giving some meaning. If we left it out then we wouldn't know something about the apple. So I suggest you shelve the idea of meaning and dependent clauses.
Actually, for GMAT it's better to think in terms of modifiers and core when analyzing sentences. Think of the "core" of the sentence as being 'The apple was on the table.', and the phrase 'which was red' as giving some extra information about the apple.
Further, when we're assessing semicolons, consider whether the sentence could stand alone (although I think you're doing this already). I could say 'The apple was on the table.' just fine as a complete sentence, but I couldn't say 'which was red'.
As for pronouns, remember that in GMAT SC we only see one sentence, so that the antecedent of the pronoun needs to be present
in that sentence. No such rule is needed for ordinary English. Clearly I can use a pronoun to refer to something from a different sentence, meaning that a sentence such as 'He was a good worker.' is totally fine as a grammatical construction. The real issue is whether
the meaning is clear. Obviously words like 'which' or 'whom' are governed by stronger rules - you couldn't use one of these to refer to a noun across a semicolon.