A) This is settled, the degree to which it is isn't. I think the current estimates are around 20% slightly positive to slightly negative but easily dealable, 10% likely to be catastrophic, end of civilisation as we know it. The most likely outcome is something between those two extremes. More in importantly there is very high probability that will cost us more to do nothing in the long term.
B) What is settled is that reducing the amount of CO2 we burn will effect the distribution of probabilities of the outcome. Ideally we should phase out coal power as soon as it is practical to do so and we should invest resources into trying to make it practical earlier.
C) What is settled is that the ice is retreating. The preponderance of evidence points towards global warming being the culprit. Nobody knows enough to give you a year. When you hear these statements they typically are prefixed with "If the ice melts at the present rate".
D) This is settled. How much by we don't have a good handle on. What we can say is that all other things being equal warmer oceans will produce more extreme versions of some types of weather event.
E) What is settled is that there are multiple tipping points. What we don't know is how much warming will trigger them. The tipping points that we know about involve the melting of large sheets of ice and the destruction of certain ecosystems and extinction of plants and animals in those ecosystems. Sensitivity is still being debated so we don't know overall how much the effect will be - refer back to A) for a distribution of probabilities.
F) refer back to A)
G) not settled - but refer back to A)
H) This is pretty much settled, it's also the wrong question. Global Warming not only predicts that the planet will warm but predicts it will do so with a very distinct pattern. Different sources of heat will have different patterns of warming. These "fingerprints" include, troposphere warming but stratosphere cooling, significantly more warming towards the poles, more warming at night than in the day, centres of continents warming more than the edges. It is possible but extremely unlikely that a different heat source would produce the same fingerprints.
We have a pretty good handle on the changes that cause the shifts in climate on a geological time scale and we are measuring most of the other possible candidates directly (output from sun, the earths orbit, position of continents).