I note your expression "the evolutionist", singular but referring to all who accept evolution. It's an insidious grammatical variation which implies that since they are all alike, there is effectively only one to consider. Historical parallels include "the savage", "the Jew" and "the Hun". Consider the prejudices of the people who used those.
1) Here is what Gould meant. The division between human and ape is arbitrary, based on a consensus of zoologists. They drew a line in the progression and called everything after it "Homo". Just this side of that arbitrary line is what we would call a very apelike human. Just the far side is a species considered a very humanlike ape. Every species on the line can be considered a transitional species between those either side of it. (I'd like to know what your definition of "transitional species" is, by the way.)
We are immediately descended from only one of the humanoid species, in the same way that an individual can only have one set of parents. Though some of them like Neanderthal Man split off as our umpteenth cousins, many of the species found are our direct ancestors, and the ancestors of our immediate ancestor species.
The current estimate is that 90% of all species of anything which have ever lived are now extinct. It happens, especially when a species very like you but somehow better is suddenly sharing your resources. Through competition and natural selection, each species on the timeline is likely responsible for the extinction of the one before it, including Homo sapiens. The other apes survived by diversifying to the point where they weren't in competition with our ancestors anymore. For example, some came down from the trees and some didn't.
2) Blue whales are very big, and they grow quickly. Cells are very small, so if a big lifeform grows quickly, a lot of cells are created very quickly. If cells multiply and increase at a rate faster than one cell per second, then it is reasonable that something with more cells than seconds since the Earth's formation (1.5 * 10^17) could fully form in the time since the Earth's formation.
As it happens, the rate of increase of blue whale cells easily exceeds 100 million per second during childhood, which allows an individual blue whale to grow to adulthood in a matter of years. Is there an actual problem with this, or does it just strike you as amazing and therefore impossible without divine help?
Ernst Chain's objections to evolution (as told by the Institute for Creation Research) have been answered many times, though not necessarily here.
- He saw evolution as a chance process, which thanks to the mechanism of natural selection it is not.
- He doubted the efficacy of change through mutation, which has been repeatedly demonstrated, most recently by Richard Lenski's e.coli experiment.
- He contrasted "classical Darwinian ideas" with the function of genes, knowing that Darwin and his contemporaries had no idea what genes or DNA were. Post-genetic neo-Darwinian theory, which was available to Chain if he wished to study it, takes genetic function into account very well.
- He saw the development of mathematics, poetry and other exclusively human abilities as the result of a "divine spark", whereas evolutionary psychology has excellent explanations for their development.
- He wrote that evolutionary theory "does not allow the development of ethical guidelines for human behavior," assuming as many religious people do that anyone would want to use it for that purpose. There's enough secular empathy, convention and philosophy to do that already, without also trying to exploit a simple scientific explanation of a physical phenomenon, thankyou very much.
If there's no particular reason why Chain did not support evolution which stands up today, invoking him is simply a shallow appeal to authority. If that's all you're going for, fine, but it's an authority in the minority.