as to 2.
Unfortunately I still haven't seen any MiFi that supports all the global UMTS frequency bands. Instead they either support American bands (850 and 1900MHz and/or 1700/2100MHz) plus the short-ranged European frequency (2100MHz) or only European ones (900 and 2100MHz). The only devices that besides both European frequencies support at least one American one are one specific version of the Huawei E583C and the Vodafone R201 (an OEM device also built by Huawei), which support UMTS900 and UMTS2100 for Europe and UMTS1900 (the latter being used in urban regions by AT&T and T-Mobile in the US).
So if you want a device that will be useable back in the States, look for the Huawei E583C with UMTS 900/1900/2100-configuration or the Vodafone R201 (which comes unlocked and will work on any network).
The other issue is that you will hardly find an American seller who sells MiFis targeted for the European market. So you'll probably need to order a device from Europe or Asia if you want UMTS900-support which would provide best coverage during your trip, especially in the Nordic countries.
This is the only seller of the Vodafone R201 I could find on eBay.com:
Portable Vodafone Huawei R201 HSUPA 3G WiFi Router Tri Band Supported | eBay