A low tech way of coping with a book like Harri Potter is of course simply to have a copy of the English original to hand, readily available (I found one in a Charity shop for pennies, as our old copy had walked).
Kind of like using a parallel text (use of which has a long and fairly distinguished history in language learning) except that of course it’s not actually parallel text so you have to do a bit of juggling.
Can be quite effective, depending on how literal the translation is.
But back to the original questions or some of them:
What are your biggest challenges?
Lack of opportunities to speak to native or very experienced speakers. Maybe the new permanent hangout will help, although you can’t really beat face to face, if that’s at all possible.
What has come closest to stopping you learning?
Thinking that it’s all just too big a mountain to climb. The remedy here I suppose is just to take it one day at a time, one step at a time, and have mini-goals which are achievable.
What makes you think you might not succeed?
As above, plus a shaky memory and dodgy hearing.
Are your main challenges different now to what you felt at the beginning?
Interesting question. I can’t think of anything significant though.
Was there anything that held you back from getting started?
Before SSiW, looking at any book about Welsh grammar just made me think it wasn’t worth the effort of starting. SSiW just banished all those fears for me, and made it possible to think about starting. Avoiding (explicit) grammar is one of the best things about SSi(W). And of course, lots and lots of speaking is the next best thing about SSi(W), because most other systems don’t really get you speaking in quite the same way. Michel Thomas maybe, up to a point. Haven’t tried Pimsleur, but anyway, that’s expensive and I doubt if they do Welsh.