i) bit of a tough one, as you wouldn't expect a 'trader' to have...

i) bit of a tough one, as you wouldn't expect a 'trader' to have the kind of holding period to be involved in a buyback, but it is possible, it would be on revenue account for a trader, and an investor it would be CGT, imo.
Dividends yes are treated the same way as it is a particular income type, you can't apply the same logic to the scenario above, investors or traders declare dividends in the same mannar.
ii) 45 days, but as previously mentioned, small shareholder exemption for credits <5k

Someone touched on this before, but it is possible to hold some shares as trading stock and some as investments, under an audit you would have to come up with why you have treated them in this way, which must be logical