Need an explanation re: xeno birth scene Alien Covenant

HI there, I am new to the forum and have been thinking a lot about some AC questions I have having seen the movie 2x already.

I guess my first question is about aligning the births of the AC xeno with the birth of the xeno in Alien (1979) I was thinking mostly about the perfect organism component as voiced by I think both Ash (79) and David (2017)

My understanding is that the xeno takes on aspects of the hosts dna- as seen in Alien 3 both dog and cow * (directors cut) and even to some degree with the Deacon in Prometheus... More on the deacon in my q below.

So how is that a fully mature looking infant xeno was birthed out of billy crudup in A:C but in 1979 the infant is pink and skitters off as opposed to standing on 2 feet. Both seem to mature fast but the AC xenos and news seem to mature that much faster. I would have preferred in some way a line from David about the Non human hosts causing his perfect organism to age prematurely- ie dog and cat years vs human years, and that the human contribution to the DNA extended the length of the life- the same quest that Roy Batty and the replicants in Blade Runner were after...

I recognize there are anomalies still to be explained like the crash in 1979 movie being 2000 years old, and the multitude of eggs and the protective barrier etc...if David has just created them and for them to be found in 15 years- seems a continuity issue- unless we have wormholes etc and that the crash shipped has something to do with David or Walter in some capacity. 

Another Q is about the Deacon, if the trilobite and the Engineer are bigger than human does it stand to reason and adult deacon with both engineer- holloway and shaw DNA, should be bigger than a standard alien- with some different physiology thrown in; including birthing.if Ridley Scott's vision includes JCameron's queen couldn't this Deacon become a queen? Or is that too much of a stretch?

I also wondered what others thought of David watching his prized possession face off vs Tennessee and Daniels when he could have ensured their deaths, kept his xeno alive and commandeered the ship anyway- unless it is more important to show how deviant and cruel he is, re: Daniels.

When he attacks Daniels on Engineer home world he does say that she will get the same treatment as Shaw...SO it would appear that Shaw was his experiment and he enjoyed it, rather than pitied her...just my thoughts...