1 Are these episodes all anime original?

I was so impressed when they decided to end the series rather than go with the filler route after they caught up with the manga.

If I remember, the manga did the eternal flame arc after the contest. Did they do that yet in the series? I stopped watching after Frosch does his walkabout, but you seem to like these episodes so I will give them a try.

2 This whole arc seems to be anime-original. No sign yet of the eternal flame arc; presumably it'll be after this on is complete.

3 Fairy Tail's viewer numbers had been trailing down for a while, so putting in a full year of Filler would have not made a lot of sense.
It also gave them a chance to work with Mashima for where to insert some space to add filler.  Which, as strange as it is, most Fairy Tail filler is significantly better than most series.  That's been one of its saving graces.

4

As far as I know there was no anime-original filler in the first series. They stuck to the mangas and quit when they were at risk of catching up to the edge.

It was kind of a strange place to quit, actually, but I guess reasonably satisfying (just after the battle of 4 dragonslayers).

They also didn't quit production during that year; they made a movie.

I think this arc hasn't been bad, but it's a bit weird and I fear what it might mean for the long-term continuity, in terms of the relationships between Lucy and her spirits.

5

Maybe it won't be a problem. One defining characteristic of Lucy is that she doesn't hold grudges. She's very forgiving and very caring. Erza has noted this; Lucy was worried about Flare during the tournament, and Erza comments, "You're a good person." Likewise, if there's anyone against whom Lucy would hold a grudge it would be Gajeel, considering how he abused her during the war between Fairy Tail and Phantom Lord, but there's no sign whatever that she does.

So once she's reconciled with her spirits it's believable that her relationship with them won't change.

Lucy is not just the audience-viewpoint character in this series. She's interesting in other ways, and one of them is the way she gets along with everyone. There are people in the guild with grudges against each other, but Lucy likes everyone and everyone likes her. Even Juvia likes her, while at the same time begin intensely jealous of her.

Lucy is part of what fans refer to as "Team Natsu" and she contributes a lot to it. Erza formed the team mainly because she wanted to get Gray and Natsu to stop fighting each other. Lucy ended up being in the team by happenstance, because she was already campaigning with Natsu and Happy. But it soon became clear that Lucy was an important part of the team chemistry. She's the weakest of the original four, but she tries hard and does as much as she can, and doesn't complain. And her main contribution was to the interpersonal relationships of the team: Gray and Natsu hated each other and they were both terrified of Erza, but Lucy liked them all and they all liked her. And that eventually helped soften all the antagonism everyone else felt towards each other, so now at the leading edge Natsu and Gray are over it.

After Wendy joined the team, Lucy continues to be important. They're all nice to Wendy, and care about her, but Wendy has special relationships with Natsu and Lucy.

Natsu is another dragon slayer, of course. She's been watching him, seeing the different techniquest he uses and figuring out how to do the same things with sky dragon magic. When she first joined the team she didn't have any attacks at all, but now she does the breath attack, wing slash, claw, and a couple of others, all of which are adaptations of things she's seen Natsu do.

But Lucy is her big sister; they're close in a way I don't think Wendy is really close to anyone else. They hug each other when they're happy, and I don't think I've seen Wendy hug anyone else (except Charle).

Lucy is like that, and I think it's foreshadowing something. (more)

6

In the manga, we're in what seems to be the final arc, and a lot of "Chekhov's Guns" are finally getting deployed.

One we haven't seen yet is Lucy's "One Magic", which she discusses with Capricorn in anime episode 153.

Lucy: Hey, have you heard of the "One Magic"?

Capricorn: The magic at the beginning of all magic, yes?

Lucy: That's what Hades said he wanted to get. I heard about it from my mother, too, but it didn't sound dangerous or have anything to do with Zeref or some "World of Great Magic".

Capricorn: What are you trying to say?

Lucy: If the One Magic that my mother talked about is the truth, Hades could never have gotten it. It's something you can't even imagine. At first glance, it seems easy to obtain, but it's very difficult, and even while it's a strong power that certainly surpasses everything else, it's also a very weak power. My mother told me that all magic starts from love. That's why I think "One Magic" is actually "love".

Capricorn: That's a wonderful interpretation.

Shortly thereafter the Spirit King invited Lucy (and her friends, but it was really about Lucy) to the Spirit World for a party, during which Lucy came to forgive her father. I've long thought that it was really about clearing Lucy's heart. And I think that soon, now, Lucy is going to discover the truth about the "One Magic" and learn to use it. Maybe that's what's going to happen with Mavis, any time now. I don't think it's possible any more for Lucy to hate anyone. Even the demons she was fighting, she fought for her friends but she didn't hate her enemies. (When one of the demons blasts another in manga chapter 384, Lucy expresses concern for her.)

Lucy has always been like that, and I don't think this was accidental. It's going to be a plot point.