Learn English – Which is correct in this instance – “meaning that I got” or “meant that I got”

A couple of things.

What I was asking was whether...

would be clearer and more idiomatic than what I meant was whether...

There is no rigid rule that absolutely requires the tense of the whether-clause to agree with the past tense in the main clause, though such agreement is good. When it doesn't agree there are consequences.

What I was asking was whether that's correct or not. ^{conversational / colloquial}

What I was asking was whether that was correct or not. ^neutral

What I was asking was whether that would be correct or not. ^{perhaps a tad more polite than neutral}

He forgot the present he had bought for Mary, which meant that he had to go back home a second time.

In this sentence "which meant that he had to go back home a second time" is a non-restrictive relative clause, and its antecedent is the entire preceding clause "He forgot the present he had bought for Mary." The which refers to what is described by the preceding clause, the situation that "He forgot the present he had bought for Mary." And yes, non-restrictive clauses are usually set off by commas.