What's the weakest link in my stereo set up? I live in a townhome, so limited on space.

Seems like you have many sound reflections. High ceilings and hardwood floors. You should do a clap test to see how bad your room echoes. Then start treating room accordingly. You may need to deaden a few areas since sound is reflected 20 ft up? So walls and floors may need absorption; area carpet, heavy drapes, etc. if you have windows that’s another hard reflection. Read up on sound absorbers and reflectors.
That could be a start to improving sound without buying equipment yet. 

@vrikkian room treatment and the addition of a sub are 1a and 1b.  You can experiment with room treatment with pillow’s, throw rugs, blankets and other various items.  Google / hit up some forums with threads, it will give you some solid, creative ideas that you and your better half can likely both live with.  On a sub, I’d reach out to 2-3 different manufactures, distributors for advice.  SVS, Crutchfeild, The Music Room, Upscale Audio.  Ask for their advice based on your placement, space limitations.  If there isn’t a solid solution found for a sub then look to sell the Focal’s and focus on bookshelf speakers known to put out solid low end performance through clever design and engineering.  Buy used, you might be able to stay on budget with the sale of your Focal’s.  Alta Audio Alyssa’s are an example of bookshelf speakers that can really fill a room, have a surprising low end performance.  There are other brands, models that can do the same.

If you then get pulled down the rabbit hole of upgrades, I would focus on your amp first.  You can use the Cambridge as a streamer, DAC, Pre and feed a standalone Amp that if you upgrade your speakers, would be the next best step.  It would maintain the ease of use of your current system, outside room treatment would check the biggest influencers on performance, speakers and how you feed them. 
 

DSP / Room correction was also recommended, you could look at something like the Wiim with DSP / Room correction, inexpensive little unit that can stream, has a DAC and most importantly has DSP / Room Correction, really cheap entry into exploring if that makes a big impact and could help you figure out how to room treat which is an overall better option than DSP.  I’m not sure if your Cambridge is a Roon endpoint, you can also do some DSP using Roon, you cloud research that and trial it for free.  That would take more work and either your ability to figure out how to adjust the frequency responses to offset shortfalls of your room or having a 3rd party design some filters for you.

As your system sits right now it appears to be well matched, balanced.  I can’t speak to the synergy which is key but on paper, you have done a nice job matching components that should compliment each other.  Strongest portion of your system seems to be your vinyl set up, that’s probably the last portion I would look at.  Tempting to tweak the set up but you likely need to upgrade other components first to really appreciate the incremental improvements you’ll get from the incremental changes, improvements to your TT, vinyl set up.

1st: I completely agree, simply change the stylus on your MP-150 Body to the 500.

https://forum.audiogon.com/discussions/who-is-using-nagaoka-phono-cartridges?highlight=nagaoka

Are you able to align/calibrate your cartridge? Near KAB? I'm walking distance from KAB in the Sleepy Hollow/Netherwood Heights historic district, Plainfield, NJ

excerpt

"knotscott

I picked up a Nagaoka MP-150 last spring, and added the JN-P (MP500) nude line contact stylus on boron cantilever to it, and think it’s spectacular. Incredibly musical with beautifully refined detail, amazing midrange clarity and separation. It sounds like I have wanted all my other carts to sound since getting into this in the early 80s. All in for ~ $570...not cheap, but not outrageous for the sound I’m getting"

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next, maximize imaging by improving initial sound wave distribution/reception. create a virtual system on this site, post some photos, so the ideas of across the width or down the length and your equipment/furniture/you didn't mention video? are easier to understand, suggestions will be easier to make and understand

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future changes

speakers, I would forget all/any subtle modifications for now,

re- arrange things so you can have larger speakers, 3 way placed/aimed best toed-in/tilted back to minimize floor/ceiling/side walls reflections (slanted face design/mid height on slanted stand/ or taller floor standing flat face slanted back to aim tweeters at seated ear level)

my assumption/guess: a small 5.1 home theater/music combo system, AVR with FRONT pre-outs, does the Cambridge have a home theater bypass input?

room treatments, maybe, but start simply with an easily re-positioned area rug

Toe In Alternates, Stereo and Video

IF open to used speakers, let us know where you live so we can look for suggestions near enough to allow you to hear them when you pick them up.

Sub for townhome might bother your neighbor,space is a problem too. I will stick what you have. Enjoy the music.