I travel domestically and internationally with my power packs in my carry-on luggage and have never had a problem. Lithium batteries are generally not allowed in the checked baggage.
There is a difference between Injinji liners and socks. You can wear the socks alone but the liners are very thin and probably would not offer much blister protection on their own.
If your feet get too hot a lot then consider the shoes/boots may be part of the problem.
I used a Vodaphone in Spain. Service was excellent throughout. They also had a special deal where I could call to the US after 8 PM for only about 18 cents a minute. Worked out very well for me.
Sierra Trading Post (SierraTradingPost.com) has been a good source of discounted outdoor travel gear. I have a couple pairs of pants as you describe from them.
Also, REI.com another good source.
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