I feel the Exodus 21 bit is the only one that give any kind of indication at all.

The fact that children of less than a months age weren't counted for tax purposes or for population censuses is very likely to do with the infant mortality rate. In that time it wouldn't have been uncommon to lose an infant in the early months, or especially the early days, of its life. Making someone pay taxes on them or including them in the census may have been considered premature given the possibility they might not survive.

It is funny that site uses the conquest of Midian under what the Bible says about abortion. The Israelites were taking the city of Midian and were commanded by God to kill every Midianite male, including any woman who could potentially be pregnant with a male baby, which included all non-virgins (virgins, however, were valuable for integration). It is really stretching to try to see this section as having anything to do with abortion, since it is about all out war and wiping out an entire civilization of people. Same thing goes for the Hosea passages, which are Hosea's pleas to God to destroy their enemies.

The only time out of all of those that it is talking about unborn Isrealite babies is in Exodus 21, that is the only verse in the Bible that talks about unnatural occurring miscarriage from a legal standpoint. I don't think the taxing and the census stuff says much about the value of an unborn child, other than to say they were not yet considered in the tax you owed or that they weren't yet tallied as part of the population. I can't imagine any culture, modern or ancient that would count unborn children as a number of their population, or charge them taxes.