To get from Batallia Downs you must first have went to Batallia Downs from that Glacier map. You can't come from jeuno to downs and then to galcier.

As a whm lvl 60 I had no problem exploring this area. Every mob was too weak. Use invisible if the mobs check at a lvl of easy or higher.

No, this would probably not be your best bet for exp partying if you're lvl 43. Reason is that 43 is the level where monsters here cap out, (bestiary is combining the levels of mobs here across every zone that they appear in). You'd be going after the top tier goblins and gigas in this zone, and they'd be Even Match and below for you.

If you're set on getting a party to this area to exp, however, you might have some luck in Fei'Yin, where shadows start at 43 and go to 46. Shadows link, unlike other undead, and you've gotta reach them using sneak since the entire zone aggros. They can be a nice break from the crab/beetle/mandragora rush we've all done for the last billion levels. After shadows, if you feel comfortable enough, you could try hitting the stairs to the lower level, usually you can camp near the top of them and pull Underworld Bats (lvl 50-52), but that's mainly if your damage dealers can handle not pulling aggro off the tank right before a Jet Stream.

Another option off this zone is Xarcabard, in which case you'd want to head right after you zone into the large open part of the zone to find the Gigas stomping grounds. They're roughly lvl 45-48, and if you want to you can drop the evil eyes in the same area and level range. If Gigas aren't great, you could try doing Demons in the NW of that area, they're 48-52. Demons are kinda fun if you have a Samurai along, as you can finally see what Warding Circle accomplishes.

Be advised though, talking someone out of doing safe exping in CN and heading to these places is going to be difficult at the least. The competition is virtually non-existant here, and the drops aren't bad at all, but they're harder to kill and you've gotta be playing like you're actually awake at the keyboard. Good luck with it, though, forming a group like this is a real good way to break up the monotony of levelling.

Eldiem Necropolis is in Batalia Downs, not the Glacier

The entrance from the pass connects in E-10. You exit into the glacier at F-11.

Theres a quest in San'D'Oria's castle for a map of the northern regions, whatever that entails. You need relativly high SanD fame, and a piece of derfland humus (drops from doom scorpions in crawlers nest). I haven't done it yet so I'm not sure what the map is of, other then its north of SanD.