On the Cork Irish website I see he gives alternative Dependant forms for Aimsir Chaite Téigh.

http://corkirish.wordpress.com/verb-conjugation/teim/

But I cant find them spelt like that in any dictionary, including his own. Nor any pronunciation audio.
Is it deaghaigh pronounced very differently from deachaigh ?

And if its an alternative past tense dependent form would it be

Ar dheaghas or An ndeaghas
níor dheaghas or ní dheaghas
gur dheaghas or go ndeaghas
nár dheaghas or nach ndeaghas

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Bíonn rudaí maithe mall

Deaghaigh is essentially the Munster form of Deachaigh. A good few Munster texts have that spelling, for example (unedited) versions of Tomás Ó Criomhthain's books. However it isn't really used much.

It takes present tense particles like other past dependent forms, i.e. An ndeaghas.

I don't know if you know IPA, the pronunciation is basically die-g, with die pronounced like English.

Although it is far more likely for somebody to say gur chuas, rather than go ndeaghas.

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The dialect I use is Cork Irish.
Ar sgáth a chéile a mhairid na daoine, lag agus láidir, uasal is íseal