It doesn't make any grammatical sense to say 'Thanks to yourself', but there are some native speakers who say this. Some people imagine that 'yourself' is a slightly more respectful version of 'you' when it occurs at the end of a sentence, so they use this in situations where they want to appear polite. You occasionally hear company employees addressing customers this way, even though this isn't correct, strictly speaking. Should you use this form? No. 'Thanks to you' is fine as it is. There is no need to alter this phrase.

No. Most people wouldn't say that. Best way to say it is "I did it thanks to you". :)

In Ireland it is usual colloquially to use reflexive pronouns instead of subject/object pronouns. It is often emphasised with 'good' - so you say - 'thanks to your good self'. If you want to offer someone a drink you say 'I'll have one- and yourself?' In rural areas 'Yourself?' is an informal way of asking 'How are you?' I don't know if it happens in other English speaking areas. Maybe this is the context you saw it in.