I find it a little confusing that "dd" makes the english "th" sound but some words like wyth are spelt with the "th" anyway
I think that 'th' is generally a slightly different sound from 'dd'. Sort of 'think' versus 'then'.
Yes. The Welsh dd is the "voiced" sound found in English words like "then", "there". The Welsh th is the unvoiced sound found in English worlds like "think", "throw".
You Are Correct, I Found This Out From The Website For A British College Or Something Like That!