If any of you all have been waited breathlessly to see how this trip worked out, the short answer is that traveling with a misspelling on my booking turned out to be fairly easy after I'd spent all that time dealing with the travel agent and United.

• Check-in at IAD took all of two minutes, after which the agent handed me boarding passes for both legs, relieving me of my worry that I'd have to repeat the exercise with airBaltic at AMS.
• I couldn't use TSA Pre, but the TSA agent at the regular line seemed unfazed by my situation aside from looking at my face and my passport more closely than I'm used to.
• The people at the Capital One lounge didn't even look at my boarding pass, while at the United Club I had to show my passport to the person at the counter in addition to my boarding pass (I assume she looked up the reservation, because this took a minute).
• The facial-recognition boarding system worked at the gate, I guess because UA did transmit the correct info to APIS.
• My Priority Pass card sufficed at the lounge in AMS.
• On the way back, I was able to check in online for the airBaltic leg from VNO to AMS but, understandably, not the UA leg from AMS to IAD. So I had to wait about 10 minutes on a line with people checking bags to have a rep handle an IRL check-in for that leg.
• Which happened to be in Polaris, because after seeing how empty the flight was looking I opted to take a cheap buy-up to PE and then throw PlusPoints at it, after which the upgrade cleared more than a day in advance. That meant I could enjoy the Star Alliance lounge at AMS just by showing my boarding pass.
• At the gate at AMS, the rep looked at my passport but I guess didn't notice the misspelling. That was one time I felt like I caught a lucky break.
• Weirdest moment of all: Global Entry worked like usual at IAD.
• Time for United to respond affirmatively to a request submitted via the form on their site for RDM, PQP, PQS and lifetime-mileage credit: four days.