SIN knew everything about Ella and her plans and they totally OK with thatAnswer 1)
Evolutions can happen at any time. There is no rule saying that the next evolution will take longer than the previous one and we have examples showcasing it. Based on the trend from the previous evolutions, a fair expectation is that MC will reach his fourth in around 80 in-game days, although that can mean anything in real time.
I don't think people expect that the 4th will come quickly, but it's already mentioned in game (in relation to Gillibrand), so we discuss it.
Answer 2)
I think people confuse SIN with Ella's faction. These two are not the same. SIN is the superhuman branch of Langdon's operations that was facilitated by Ella as part of a business agreement. Currently there is absolutely no reason to support SIN. Joining SIN does not equal joining Ella. Unless of course people have a hard-on for Jared and want so much to work with thim or something.. dunno.
If we are talking about Ella's faction specifically, Ella wants to buy time to do whatever she needs to do. Love her or hate her, her work seems to be important, even if she clearly is a villainous character (same can be said for HERO members btw). We don't know the why, we can only speculate MC's part. But she has a "supporter" named Lochan Deus, who can see the future and believes that her work will fix a "mess".
SIN act as facility for her band (all medicine )
SIN take a lot of help from Ella
Members of Ella gang are now actively work with SIN
.
So they are at least ally and take responsibility for Ella actions