Riri_san
Still think Slytherin's the best, first of all as I had mentioned in the previous chapter along with the fact that in this chapter he mentioned he needed both money and power for a peaceful life, I do not know what power you are talking about here whether political or personal power, but for both political power and money you can't get them in any way in any other house, let's be honest not a lot of people from other houses are gonna matter later in the grand scheme of things(not plotwise but career-wise), sure there are the occasional few but compared to Slytherin they are nothing. Snape would be half a problem less, other teachers might not like you but they wouldn't be openly unfair as snape. And if he needs stability later he needs a show of power for that, Slytherin dorms would be the best chance for that. I am not saying he needs to be part of politics but strength automatically makes you have others want to be connected to you in some way and with him being wealthy, it would almost be guaranteeing him a comfortable life. With him being in other houses first would be the social isolation and bullying he would get from him being the son of 2 death eaters convicted to Azkaban, sure with his power he wouldn't care but why go through all that when not needed? And not just the three houses but even Slytherin would join in since he was not up to standards for purebloods or something. Second would be the problem with his mother, that would need a whole bunch of bs to make sense of her being ok with a non-slytherin child, Sirius was pretty much disowned for that. I can list many other reasons but these are the main few.
about harem ... huh since you are new autor i would tell you that harem writing is very hard to make it good unless your are skilled in the genre , most harem story end up as trash since autors cant make the wives live as more thant a 2d npc with no storie and plot holes you can try 2 wives one for each house he got at most i guess if you really want to go that way but please develop their characters to be more thant trophy in a pokemon harem lol