Just been looking at some old postcards from around the same year.
I think you can safely ignore the "sutterlin" sidetrack as this is normal, British English handwriting for the period. I think that sidetrack got started with the thought it might be "Hans".
About Ancestry - it's data isn't very complete, it's riddled with errors, and it's a very poor way of researching family trees. It can give a start, but everything needs to be confirmed against the genuine sources.
On a separate track, have you identified Jack's regiment?
Does it make sense to you that that Arthur is a "sensitive boy" but living within the Army routine at home?
The Maisie referred to appears to be in Egypt too. Does this make sense?
Whoever the letter writer is, he sounds like a close family friend. There's a lot of familiarity "our Jack", he has independent correspondence with at least three members of the family (Ada, Jack and Maisie - although he's possibly talking to Maisie face-to-face rather than corresponding).