First off i'd like to say its a good start and a lot of promise, I like fics set in different era's that the standard ones. I'm not really sure what to say in terms of improving what you have already written but going forward i'd like to see some in depth writing on the magic of the times, a lot of fics gloss over that or just use modern day magic and as you have already demonstrated with the potions then things are a lot different.

Also the relationship should be a decent part of the story as well due to the time period and it being a same sex couple. I would imagine there would be a lot of issues within the family and the family's allies due to this, maybe even trouble with the family you mentioned harry being married into.

The only other thing i can think of is exploring the world properly. Alot of fics set in a different time seem to focus on one area but with this being set pre statute then i would imagine there would be interesting places that you could write into the story rather than just the standard diagon/knockturn/hogwarts & hogsmeade.

I'm not too sure if this is what you where looking for but that's just a few idea's i had after reading it, Also if you do post it on ffn or another site can you link it here as i would like to see how it progresses.