Great fun isn't it... I get lost unless I draw little pictures for myself but getting old I am still a bit lost... So correct me if I am wrong with my thinking .... what you have is....
Christy McInnes (circa) 1780 - (Any idea of maiden name and husband..

was it Angus???)
had son Donald who married another Christy who was a sister of Rachel. In 1851 he was head of house caring for niece Margaret 18 living with him? with wife Christy dead (he had remarried???)
Donald's son Neil was living close with an uncle Malcolm
Maol Caluim - Malcolm McInnes (who married Anabella McPherson) was or was not a brother of Donald McInnes

? If he was it would make Christy (circa 1780) his mother

? and was Angus the father

?
Was this one of the Angus's in Black John's family of:
Calum Mor - Malcolm the Elder c1765 (m) Flora McKinnon c 1772
Neil c 1766
Aonghus Mor (Angus the elder)
Myles c1769 (m) Marion McKenzie c1768
Calum Og - Malcolm the Younger - 2 sons evidently migrated Australia
John (Jonathon) (m) Isabella Anderson
Aongus Og (Angus the younger)
Hope I am not confusing just trying to understand.. Thanks Clint