I’m always very pleased to hear when Course 3 does something to earn its keep (since I don’t think that in general terms it was a particularly good piece of course building)…! 
That’s Course 2 material, so you’ve got two choices - keep on doing the work to get the others really drilled into you - or cheat a little by asking on here (or Google!) what chi, ni and nhw are (oh, oops!) and then practising using them with the structures you already know…
I’d recommend waiting until we introduce them, though, to be honest - if you don’t have an urgent need, and it’s just about how well you feel you’re doing, then trust the system…
That’s true insofar as how most people would choose to ‘translate’ them into English - although I wouldn’t usually suggest ‘to be able’ for cael - but then you’re into deeper waters once you start thinking about how people tend to use bits of language.
For example, there’s a (pretty old-fashioned now?!) pattern in ‘home counties’ English where if someone makes a statement and you want to agree strongly with them, you’d say ‘Oh, I’ll say!’ (hard to get through an episode of Jeeves & Wooster without it)… 
Clearly, this doesn’t actually mean ‘I will say’ - it means ‘I agree’.
So, ‘gewch chi weld’ is indeed the future of cael, rather than the future of gweld - often, ‘cael’ will give the sense of ‘you get to [x]’ (but it’s vital to remain aware that languages do NOT map perfectly to each other, so it doesn’t work well to try and treat nuance in your new language by mapping it to your old language).
You’d hear ‘gewch chi weld’, for example, in a slightly challenging or threatening way - ‘o, gewch chi weld am hynna’ - but the key here is that this is a tone which comes from usage far more than from ‘meaning’.
Which leaves me where I started - ‘gewch chi weld’ and ‘mi welwch chi’ (etc) are close enough as makes no odds - for learners, using whichever comes to mind first is the only rational approach, until your exposure to the language gives you a more nuanced sense of when to use which…
