Though

I use the word 'though' at the end of a sentence instead of 'but' at the beginning. As in:

You're good. He's better, though.

Can 'though' in the middle of a sentence mean 'but'?

You're good, though, he's better.

I think that 'though' in such cases means 'although'. Am I right?
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You're good. He's better, however.
Is 'however' more formal in such cases? Is it used in everyday conversations?

You're good, however, he's better. - Is this possible?
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One more question about 'however'.
I use it at the beginning of a sentence that isn't related to the previous mentioned sentence. As in:

You're very bad at this. However, keep trying and you'll get better eventually.
Can anyone tell me how to use the word 'however' at the beginning of a sentence?

Thanks.