You're close, but I'm going to break it down just a little bit, and see if I can help with this. I'll start with person A:
好きな子- A 'child' (subject) likes. As you have noted in your translation, they aren't talking about a child, but rather a girl, as this seems to be a conversation between two boys (teenage boys don't get called 子, but teenage girls do). The subject of this sentence appears to be person B in this sentence.
ぐらい- At least (see definition two at jisho.org)
は- Topic marker, this specifically marks 好きな子, or the girl that person B likes.
いるんじゃないですか- Don't they exist? This is similar to saying 'Is there not....' in English.
So my translation of person A:
(Speaking to person B) But isn't there at least someone that you like?
If someone were to be liking person B instead, you would see something to the effect of 'あなたのことが好きな（人/子）', so the direction of the liking is definitely coming from person B.
Now to break down the response:
そういう- like that
の- nominalizer of そういう to form the phrase 'thing like that.' Thing in this case can be exchanged with person.
も- this も behaves kindof like 'even if,' but it really just depends on the circumstance. Here's a good explanation of the も particle.
含めて- the て-form conjugation of 含める, or to include.
分かんなくなりました- Became so that I do not know. You probably noticed the slurring of the ら in wakaru. This is fairly common in daily speech.
So my translation of Person B's first line:
Even if there was someone like that, I can't tell any more.
The last line you had pretty good, but you put a negative connotation on it that I don't really think is there. In English, 'It's not like...' uses sarcasm, which is very rarely, used in daily Japanese conversations. It gives a negative connotation to what is being said. I'm not getting that feel.
誰も- No one
僕の話- My story (more like 'what I have to say'). This is the object of the sentence.
を聞いてくれる- Will give of their listening to (object)
So my translation would be:
It's because no one will listen to what I have to say (about the matter).
I included the 'about the matter' in parenthesis because it was implied, but not specifically stated. In English, you have to make inferences in the translation, especially when taken out of context. This is one of those cases where I think that it might be useful to include it, but you can probably get away without including it as well. Just depends on your preference.