As for handlebar height, on my touring bike I like to have the tops of the bars at about the same height as the top of the saddle. I've heard many tourists say the same, but obviously this will vary based on personal preference.

Your saddle height doesn't look high - not very much seatpost exposed. Especially if you consider that the LHT has a slightly sloped top tube. The Rivendell standard of a fist of seatpost exposed assumes a frame that is built with a level top tube. Since the LHT top tube slopes up a bit as it goes forward, you can have a bit more seatpost than a fist's width exposed and still be within that sizing metric. With steeper top tube slopes, the fist width metric makes no sense.

Your pants inseam of 30 and pbh of 80 (31.5) sound reasonable. My pants inseam is 32 and pbh measured wearing cycling shoes is a little over 34. You should measure your pbh while wearing your riding shoes, and also guage your standover clearance on the bike while wearing riding shoes. It sounds like the 52 fits you pretty well (I certainly wouldn't recommend smaller). It also sounds like you have enough standover clearance to fit a 54 if you wanted to. The question then comes down to the distance between the saddle and the bars. Does the 52 feel too stretched out for you as it is set up now? If so then a 54 might be too big for you. If you think you'd be comfortable with the bars a little further away from the saddle, and don't mind tight standover, then a 54 might be a better fit.

Personally I prefer a larger frame, so I can set the handlebars at saddle height without a jacked up stem (by bike uses a quill stem). My current touring bike has little to no standover clearance and this has never been a big problem for me, even when touring on rough roads. Again, personal preference.

Also, I'm surprised to hear that steering tube is uncut. The 54 uses the same fork, so if this one has really not been cut, then getting a 54 will not make it any easier for you to get the bars higher, if that's what you needed to do. You'd still have to do this by changing the stem.