I'm no expert, but...
1) I would X. If partner bids spades, great - otherwise I bid 1NT next. Alternatively you could bid 1NT straight off - a little off-shape, but at least you have a good club stop
2) This is a tough one :/ I would bid 3H. Partner will likely bid 3NT in which case we can bid 4NT (quantitative invite). The only alternative I see is blasting 6NT, which you may well have to if partner comes back with 3S.
3) Why not super-accept with this 17-count with
♠AKxx? Anyway, South didn't, so now it comes down to what 3C means. I play it NAT GF and would bid 4C here. Some pairs have a gadget for "fit with one or both" and this is the perfect place to use it.
Don't be afraid to ask for help here - it's what these forums are for
I have a feeling some of these would be better suited to the int/adv forum, but I may well be wrong on that.
ahydra