I am enjoying my analog system, but what can I do to improve?

Before I think about doing anything drastic like removing a wall, is there a way to quantify/measure the room deficiency? 

What do you think about the tone arm (on 1200G) or Kitsune phono stage?

I’ve seen Ralph mention that the weak links of the Technics (for MC) are their tonearm and record mat. I couldn’t agree more!

There are a few options from the UK for armboards from such places as SoundSupports & Ammonite Audio. As far as record mats are concerned, I have had much success using the current Luxman mat on Technics including your “G”.

Also for what it’s worth, the short cantilever of your Dynavector gave me a huge education on the importance of zenith (yaw). After setting an earlier example of a 17D into an SME 309 years ago for an industry friend, it just revealed an overall lack of pace & dynamic involvement. A very slight twisting in the non-slotted headshell towards the direction of less detail was able to produce nirvana. With the timing of its Micro-Ridge stylus finally “in the window” for proper channel timing, the Pace, Rhythm and Timing (PRaT) was now evident in spades.

A Kuzma 4 - Point tonearm would be a significant upgrade over the stock Technics arm. But rather expensive!

Harmonics don't stop at 20kHz and it's been shown that they can have a direct impact what we hear. Supertweeters do add the edge you are are wanting and would be well worth considering particularly if you are analog and the source extends higher than human hearing.

MillerCarbon might have been doing a hard sell for Townshend Maximum Supertweeters but a lot of what he said is pertinent.

Check any music frequency chart. There is no music up there to hear if one even could and the gear is capable. Just noise most likely. Waste of time and money but if you’ve already conquered what does exist and can be heard then there has to be something else to obsess about. So the whole you need a supertweeter to hear what’s not even there argument is shooting blanks.  If you use a supertweeter to tip up your subtle top end for more air than otherwise, different story.