If the solder is loose and you're under 30 days, go back to Sprint and exchange for a new phone. I just exchanged my Evo because the USB port completely broke at the solder point. The store gave me a new Evo even though I purchased mine back in June because they didn't have any refurbs on hand and didn't know when they could get me one. Refurbs are the policy, but they gave me a new one because the people working there had a store full of potential new customers watching me return my Evo and didn't want the attention. I didn't make any noise or scene at all, but they were handling everyone in first-come, first-served basis so all eyes were on just a few people. Definitely better than what I expected, but you should get a new phone now rather than wait.
As to the looseness of the microHDMI, mine's pretty solid on the new phone. My original phone had a loose one even though I only used it once to demo the feature. If it's loose, it's not supposed to be so take care of it now.