I don't fully understand why you would buy a refundable ticket and hold that much on your credit card.

Just buy the cheapest ticket you find for the dates you need, print out the e-ticket once UA has ticketed it (with a 016 number) and then cancel the flight within the 24 hour period. Your credit card will have a hold on it for the ticket amount but that will disappear within a day or two usually.

All the embassy needs is proof of a ticket. They do not verify any ticket. I have done this many times for many different visas. The embassy just wants to see that you are serious about going.

It looks like the EU visa is $50 while the US visa is $100. Note that the US visa applicant is forced into a multi-entry visa for $100, good for 12 months. I did this last year. If you have plans to go back to Tanzania then just use your US passport and get the one-year visa on arrival.

-RM