I wish the writers would delve deeper into the Vashoth.

I think the short answer would be none of the writers are that interested in the concept. After all, Tevinter Nights could have been the opportunity have a story featuring Vashoth, as they are more likely to be found up north, but there wasn't a single character from that background, not even in the stories featuring Grey Wardens, who you would think would be the most likely to accept them into their ranks.

As you say, it seems odd that we don't hear of ghettos where Vashoth are found in human nations that correspond to elven alienages. After all, pretty much the whole of Thedas north of the Waking Sea was once under attack by the Qun and you would think the Chantry would use that against anyone of that race, just as they do they elves. Perhaps the difference is the Qun never got as far as Orlais or attacking the seat of the Chantry in Val Royeaux. However, we do know from codices that Tal'Vashoth find it difficult to gain acceptance in human society even when they manage to escape the Ben'Hassrath hunters, so the prejudice is definitely there. It is said that most end up either as mercenaries or bandits, the former giving them a degree of acceptance and even status such as Bull enjoyed having taken control of the Chargers from their previous leader, whilst the latter are automatically outlaws so don't trouble themselves whether the wider community accepts them or not.

May be the numbers of next generation Vashoth are just too small to warrant anything more than a passing reference such as we have been given up to now. When you think about it, the majority of Tal'Vashoth tend to be defectors from the Antaam and so are going to be male. Most female occupations take place on Par Vollen, where it is going to be far harder to escape even if you want to. So, likely the only female Tal'Vashoth are probably going to be priestesses of the Ben'Hassrath travelling with the Antaam, who have come to question their beliefs, and they are likely to be seen as the most dangerous form of Tal'Vashoth by the loyalists and thus most likely to be hunted down and killed. This would mean that actual children of Tal'Vashoth are going to be rare because of the lack of females and thus Vashoth communities are going to be almost non-existent.    We have never been told what happens when Tal'Vashoth mate with another race.   Would the children favour the Tal'Vashoth parent but just a bit less bulky or would it be a case, like the elves, that the bloodline is not evident from the physical appearance?

As to your last question, I imagine that if they live a nomadic life it would likely involve tents of some sort, although this would depend on the terrain and landscape of the country they are within. If living close to mountains, it is possible they would utilise caves for shelter or if they are in a forest and plan on staying in one place for a while, may be they would create platforms in the trees similar to what we used in Jaws of Hakkon.