Translation:I do not run with my wife because she is not able to run.
I wrote "I don't run with my wife because she is unable to run" and it was marked wrong. Is this something the staff didn't think to include, or is my English just weird?
Neither the de Bhaldraithe dictionary nor the NEID seem to have a way of saying "unable" that's different from "not able", so your translation is probably fine. Try reporting it next time you do the skill?
I also was marked down for unable so I reported it as correct. I find that Duo is constantly improving and including any corrections reported. It's an evolving service and wonderful for that.
I got marked wrong because I put "ot" instead of "to"... I'd be fine if it actually changed the meaning of the sentence, but really what could that possibly be other than a typo for "to?"
Does this construction refer singularly to one's physical ability to do something or can it also refer to a conditional statement (eg: you eat your candy when/if you finish eating your chicken)?
It contains the word "ábalta", which means "able", "capable", so it can only be used in the former sense. Any reference to being permitted to do something would probably use the verb "féad": "Ní rithim le mo bhean chéile mar níl féadann sí rith."
What about in the case of asking a question like: can you help me please? Or can you pass me the salt?
I suppose those could be re-analysed as "are you able to help me?" and "are you able to pass me the salt?" Personally, I'd phrase those questions as "would you..", but I don't know the Irish equivalent to that! As it happens, the Foclóir allows for other 'can' constructions: "he can swim" can be "tá snámh aige". Check it out: http://www.teanglann.ie/en/fgb/can