The DLC ends with the family back to normal, sitting around the table. Plus from the game itself we see that infection goes from normal to straight up insane in waves (Mia). So no the DLC in no way contradicts the main story. As for the house, other than the locked doors, we already know that Lucas was some sort of killer, and that the family was in denial about it. Plus the whole place was built by George Trevor's company. Everything checks out.
It's the best story/BOW since the G-Virus. It takes from a ton of classic horror films, and reinvents the whole thing ala RE. Beautiful.
Mia is a bit of a special case as highlighted by Lucas' files. None of the other Bakers had such violent swings to where Eveline wanted them locked up. The Bakers are "normal" to where Eveline wants them as, which by her design still means violent.
That "normal" view is a still frame of them sitting at the table. There's no dialogue, movement, or anything other than sitting at a table that suggests things are normal. With Eveline present, it's just as likely of her "playing house" in her influence. The point is that the Bakers are immediately subjugated to Eveline from zero to 11, rather than the creeping realization/process shown in Marguerite's diary.
Lucas being a killer (already addressed) and the Baker's denial of his problems doesn't make the Baker parents villains with torture chambers and crematoriums. It just makes them shitty parents and ignorant people (we only know of one pre-Eveline killing by Lucas).
The Plantation estate was not built by George Trevor or the comapny that operated past his death with the given information. All Trevor & Whatever Co. were contracted for were the shadow plinths in 1993.
Even in the main story the game is inconsistent, particularly with everything dealing directly with Eveline. The DLC just furthered the issue.
Again the presentation is rather remarkable for the most part to the point where it hides some of these things. But once you start replaying and go in knowing what pieces are all on the table from the beginning, it's found that so much of it just doesn't fit.
I agree with the earlier post. Evelines plot easily is the worst RE plot. Actually I think RE has had an issue with plots in general for awhile not. That's not to say you can't have good moments in a bad plot. But the last good "for what the series is" plot was RE5.
7 has the most disjointed narrative (odd due to a series that has held its canon together throughout), but the plot itself isn't so bad. 6 still remains the worst
overall, despite Piers, Jake, and Sherry having outstanding moments and development that can't be found anywhere else in Resident Evil.