Not true. In STV jurisdictions most voters vote by party. Ireland has a higher rate of cross-party voting than most other STV jurisdictions, but that's Ireland for you. If you look at places like the 51 members of Belfast City Council (all elected by party label by STV, with only one independent elected), or the Tasmanian legislature (25 members elected by STV, three parties, not one independent) you will find strong party loyalty among voters there.

Not necessary. With STV, in a five-seater district there will be three or four NDP candidates and three or four Liberal candidates, and that voter can form a conclusion on which Liberals are too far right and which NDP candidates are too far left, and rank the candidates accordingly. That's very common in Ireland.

That's a big oversimplification. FPTP gives a great deal of power to parties, since the voter has no real choice of candidate: if you vote primarily by party as the great majority of voters do in countries with a parliamentary system, you have to vote for your party's local candidate. MMP gives more voter choice, since you can vote for the local candidate you like best regardless of party. Open-list MMP gives even more voter choice since you can choose the regional candidate of your party that you like best, as well as voting for the local candidate of any party you like best. STV gives more voter choice too, in a large STV district where your party is likely to win at least one seat. In small STV districts a voter for a smaller party may find his or her second choice getting elected, but if your party gets less than the 4% or 5% threshold electing your second choice is better than your vote not counting at all. 

STV could work federally, in theory. The only difference is the size of the districts. BC has one MLA for 50,000 people, so an urban five-seat district will have 250,000 people, which suits the size of local cities in the Lower Mainland. But with federal seats having, in Ontario, about 118,000 people each, a five-seater would have 590,000 people. That might be acceptable to voters in Toronto, Ottawa, Mississauga or Hamilton, not so much elsewhere.  

Which nicely shows the problem. With an open-regional-list MMP system, if the south half of Alberta is a region, that rural southern Alberta NDP voter will likely help elect at least one NDP MP. although he or she may well be from Calgary. With STV, a four-seater rural southern Alberta district would likely elect three Conservatives and one Liberal, so your second choice for the Lethbridge Liberal would count. No matter how you slice it, there aren't enough rural southern Alberta NDP voters to elect one of their own.

Hungary has a system which is similar to MMP, and they elect the local MP by preferential ballot. I don't know of any actual MMP jurisdiction which does this, but we might have had the first: when the BC Citizens' Assembly designed their excellent MMP system, that was a feature of it. They then voted between the two systems they had designed, and decided that BC-STV was the better fit with BC's geography and political culture.