This one's easy enough. I imagine Willow showed Fray the spacefrak and the resulting apocalypse. The big reveal, the big climax (heh) of the season is obviously #34. Showing Buffy sleeping with the 'enemy' and starting the end of the world -- that seems like the best way to motivate Fray to turn on her. What else would work? Bankrobbing? No. Fray's a professional thief. She'd probably want to talk to Buffy about how you lifted a choice piece back in the good old days. The clash between Buffy and Fray is about end-of-the-world stakes, so it makes sense to me that the vision Willow shows Fray would be about Buffy spacefrakking.
Interestingly, I find my answer to 2) is greatly influenced by answered 1).2) What was Willow's intent in forcing Buffy to kill Willow?
wrote in his review for #18: "it's quite possible that this will all end with nothing more traumatic for Buffy than getting sent back to her own time (possibly with a brief layover in cartoonland) having seen what's to come - "Get It Done" all over again."
Hindsight being 20/20, we know there was something very traumatic for Buffy to go through in #19 -- Willow forces Buffy to kill Willow. I've come up with a few theories on Willow's plan in ToYL. That plan hinged upon showing Buffy a world without a Slayer army (so that she felt her failure), forcing Buffy to fight to save her world by elaborately manipulating Harth and Fray as Buffy's obstacles, and then finally forcing Buffy to kill Willow herself in order to save her world. The endgame was always to send Buffy back to her time (that's why Gates untied Buffy).
It's such an elaborate script Willow's created to emotionally manipulate Buffy. I suspect that's the ultimate point. Willow is trying to make Buffy feel. She brings her to the future to show her how the world is less. Two ideas occur to me: 1) Willow was trying to show Buffy what a world without magic is like, only the lesson doesn't land for Buffy in the way Willow intended. 2) Willow was trying to emotionally jolt Buffy awake from her disconnection by forcing her to live through the consequences of having to kill a friend.
Buffy feels disconnected from her Slayers around #11, but she still grieves deeply when Aiko dies. Yet I have to wonder if Renee's death under Buffy's leading them right into a trap was just too much. Her disconnection becomes a willful retreat and it's even easier to disconnect from victims in a future world that's not really hers (it's not her world to protect, she's trying to get back to her own world). Being forced to kill Willow is a way to demand she face the dangerous consequences of her current priorities and there is no escape from feeling that pain -- Buffy can't disconnect from killing Willow (as shown way back in LWH, they're close even when they're apart, they're a part of each other).
The message viscerally associated with this experience in terms of Buffy's POV is: prioritizing her world and her army of Slayers leads to killing her best friend, the person who's a part of her. The triumph of the big picture at the tragic cost of personal connection.
I feel like it's not possible to take this further, that there's parts of Willow's story and her motivation that will only be made clear in following her journey post-Season 8. It seems too simple to think that Willow brought Buffy to the future in order to prevent the spacefrak and the loss of magic, partly because that would mean Willow's story is about being consumed by obsession in her need to restore magic and I feel there should be a twist here, something to subvert the obvious direction of Willow's development going forward.
So if Willow's goal wasn't about the big picture and saving the world (of magic), I wonder if it's not simply that Willow brought Buffy forward to help Buffy return back to herself, that Willow bringing her into the future was about giving her perspective on the big picture vs. personal connection struggle, cruelly demonstrating how Buffy's priorities were whacked skew by forcing her to kill Willow.
That would mean Willow's last act in the world was helping to save her best friend one last time, to help Buffy get back on track (which she'll be by #40). Interestingly, this effect doesn't come about immediately. The initial emotional backlash for Buffy is to distance herself even further from her friends. She throws herself into her Slayer duties with manic passion in #20, she avoids her emotions all around until she finally breaks down and confesses to Willow in Retreat. And no doubt it's Buffy's reconnection to her emotions in Retreat -- "I feel more" -- that enable her to resist the Twilight 'paradise' and hear Xander's call.
In looking at this I have to wonder what would've happened if ToYL never happened. My best guess is that Buffy would've continued down her path of disconnection, her moral center being chipped away by Twangel until he offered her Twilight paradise and she took it because at that point she'd lost hold of her ties to the world. Killing Willow in the future forces Buffy to passionately embrace Willow in the present upon her return. Being forced to break those ties in the most painful way imaginable (echoing her trauma in "Becoming") makes Buffy all the more eager to reforge them in her present.
So in a way, I think ToYL was an emotional wake-up call for Buffy. Willow saying to Buffy, "Look at your life, look at your choices, ow this mortal wound is all itchy, we love(d) each other -- let's not kill each other, 'kay?"
Buffy and Willow -- best relationship in the comics, I swear.