As you said, they shot themselves in the foot. It's very different from the previous shows, and as a result most of the established viewer base won't like it. It's also set very late in a universe, meaning new people are unlikely to pick it up.
Your points about SG-1:
Yes, it is rather repetitive in its locations, and the best alien encounters we got were in the fucking movie (and the, like.. 2 first episodes). The aliens speaking English is dumb, but rather required for the stories the episodes tell to be able to be contained in 30-45 minute windows, and can also be explained by them sending a translator along, who is then just dropped because his one goal would only last for like 30 seconds of each episode.
The overarching plot of the humans beating the Goa'uld is dumb, yes, and it should have come after the humans got hold of Asgardian tech (And don't even get me started on the Asgards.. Such a dumb race).
That said; it's a show with likeable characters who are likeable from the start, set in a vast universe (even if its one filled with cliche's). SGU has characters I personally find fucking annoying and want to gouge their eyes out with a rusty spoon, that skips a major part of the universe it's set in, namely the Stargates. Yes, they drop stargates down as they go or whatever, but what sold the first series were the adventures the characters had going through them.
That said, I really fucking enjoy the universe SG created, so I'll likely end up watching SGU just for the lore stuff..
Is it wrong to date yourself, I think myself and I would be great together.
I'm pretty sure the kind of time travel occurring in Back to the Future applied on a single timeline, as the storyline would have never had much weight otherwise (it's all about modifying the past to change the present/future in some way).
This said, even if you never travel back none of your actions in those past 5 minutes should somehow compromise your existence, as nothing worth noting surely happened during that time, nor anything minor changed in the past could affect you directly since you're re-joining the present later. The only exception would be the famous case of killing someone who contributed to your existence way far in the past (like a parent or ancestor) or merely preventing the conceiving of yourself or one of the key ancestors/relatives that eventually led to your birth. This should technically erase you from existence, wherever you are.
I fear the real issue would be if your past self don't travel back herself when the 5th minute comes. If she doesn't then it's like you never did and everything should just shift back to "normal" like nothing ever happened. However, your present self could theorically stay in that past time forever but so would do your past self in a further past time where she met another version of herself. In other words, you would replace her in that time.
The solution? When the 5th minute comes travel back with your past self to meet another past self. Then do it again. And again. Until the DeLorean will be inevitably full or the universe will implode. Either way, possibly before this would turn in the most messed up (and arguably narcissistic) orgy of all times.
Imagine this: you use two time travel machines simultaneously, one moving you to the future and another to the past, creating two versions of yourself. Then your future self travels to that past, meeting your past self. But your past self has already done something that changed the future and made your future self impossible to exist due to the butterfly effect... So your past self will meet a ghost, which will be able to predict its future! Then you time-travel to something a bit earlier than that future, do some changed there, return back, tell your ghost that her prediction was wrong - and... the Universe collapses into a 0-dimensional wormhole!