It appears to me that you view those atheistic biologists primarily as atheists who practice biology only to prove that there is no God or meaning. It's the other way round. The more you know about how nature works the more it is clear that there is no teleology other than a solipsistic one. So, of course the two activities go together. Btw. solipsistic teleology is at the heart of Hinduism (Maya as a "divine play") and also Buddhism (forms are empty of attributes and hence also meaning). Only classical dualistic theism and its various offshoots are obsessed with teleology.

In case of my article, what you view as a pyramid and a top-down process is in reality a circle or a sort of parallelism / equivalence. And one should probably add consciousness to the whole picture, too. So, the entire map then would read as -- consciousness is information is energy is matter is energy is information is consciousness. Of course you can start counting anywhere on the circle, the result is the same. Thus, you don't need any plan or blueprint to create such universe. You simply randomly "cast dice" until one universe sticks and then you experience it. Truly a child's play.

As for random mutations -- it's in the article I linked to (here's a pdf). Random chemical reactions and natural selection are used on industrial scale in development of e.g. new drugs (as it turns out, it’s faster than targeted design). As for biology one such experiment is described here.

But the whole problem of creation and subsequent evolution is poorly defined on your part to begin with, because evolution is directed by mutation and natural selection in any case. The question is not whether there is a plan (there is none), but whether the mutations are caused by environment (which then kills off non-mutated variants), or mutations happen randomly and environment merely screens out the resulting population. You certainly don't need any blueprint for any of that as the system checks itself automatically and what comes, simply comes.

So, the whole thing can be summarized like this: there was no plan to create humans, but given the initial configuration of this particular manifested world, humans were inevitable. Thus, the meaning of your life is your life.

Now, again Brahman -- how something not a person is indeed personal? Simply speaking a person is an object. Brahman obviously cannot be confined into such narrow category as it is all that is (existence). That would imply that Brahman is impersonal. But Brahman is that why you have a sense of a person, it's the first person singular perspective from which you derive your "I" (consciousness). Thus, there's nothing more personal than Brahman.

As for the need to make distinction between Brahman and Brahma. I personally feel no such need. If you ask why there even is such a concept, then it's probably to distinguish between Brahma as Brahman in motion and Brahman unmoved (and again, you cannot separate one from the other).