I will check into the links that you provide and come back. But I will say a couple of things in response for now.
It was Millers experiments that I was alluding to when I said that it has been proven that it is possible for amino acids to form randomly. However, there are a couple of extra points that go along with those experiments that are generally ignored. I don't remember precicely but this is the basic idea.

1) Miller had to carefully setup that experiment so that once the amino acids formed they could be removed and protected. Why? Because because left in the water these amino acids rapidly breakdown into simpler compounds. Exposed to the atmosphere produces the same result. So, the real world aggressively works against amino acids existing long enough to form proteins let alone cells. Interresting experiment but not proof of the method by which cells came into existence.

2) If indeed this is a model of the real event that enabled cells to form, then, I have to ask, what part of the real event does Miller, himself, portray?

3) Not sure about this (I definitely could be wrong) but isnn't methane produced by living organisms? Hmmmm, I think I might do some research on that one

With the donkey horse producing a mule example. I draw the opposite conclusion.
As closely related as they are, I see two species that are so far apart genetically that it is impossible for them to "evolve" any further.
The same thing happens with a chicken and a turkey.
So the conclusion that I draw from those examples is that genetics itself works against "evolution". Genetics itself ensures that a species cannot "evolve" into something entirely different.

Now to the fossil sequences and the "remnant" parts you mentioned. Yep I have seen those too. They were one of the things that caused me to believe evolution orriginally.
However as you say, there are missing links. There are so many "missing links" in fact, that there are probably as many differnt versions of the sequence as there are missing links. This shows that is by no means certain. Definitely not certain enough to treat them as absolute facts. Again all very facinating of course but I find it about as convincing as my earlier example. Snails evolved from pine cones.

Well, I'm off to check your links, you never know, you might have something I haven't seen...Always willing to dig into facts....lol