I have an office across the street from our building that I've just linked with two RBSXTG-5HPacD's. I want to make sure that I'm getting the best connection and speeds possible and, as point to point wireless is new territory for me, I was hoping to post some screen shots from Winbox and get some feedback and suggestions from you guys.

The two buildings I'm linking are about 550 feet apart with a direct LOS (the distance marker from Google maps actually starts and stops at the locations that the antennas are installed):

When I check Winbox my Tx/Rx signal strength is -37/-37 dBm with Transfer Rates of ≈300Mbps and Receive Rates of ≈400Mbps with an SNR of 64db:
I was under the impression that a signal strength dBm closer to zero was better (e.g. -37 would be better than -87) and that an SNR further from zero was better (e.g. 64db is better than 40db); based on this understanding my numbers looks pretty good. However, as you can see in the 2nd Winbox picture above my Tx/Rx CCQ is around 83/47 % - my understand of this is that those are pretty bad numbers.

I've seen some suggestions that lowering the transmitter power may help but when I tried that it seemed to kill my transfer rates. So my question is what can I do to improve connection quality and, ideally, what kind of Tx/Rx rates should I expect during a bandwidth test.

I've included the information that I've thought was necessary but if you need any other info to provide advice please let me know and I'll do my best to supply it. Thanks in advance.

Your Ros too old, upgrade to the latest at first

Next, your TX/RX CCQ... try to play with TX on both sites signal level and observe how CCQ is changing.

And the frequency scan is good option before setup a link.

I've included the information that I've thought was necessary but if you need any other info to provide advice please let me know and I'll do my best to supply it. Thanks in advance.

Use freq. between 5400-5500Mhz for best antenna gain.

Start by doing an spectral scan/history to determine an optimum channel selection (i.e. in a zone with the most contiguous free spectrum available).

These commands aren't available with the wireless-fp driver package (needed for AC platforms), so your best bet is to replace the 5HPacD at each end for a regular SXT once and issue
then once you locate the area with most free contiguous frequencies available, say 5400-5500, issue
Screenshots at each end will be very useful for a starting point.

You just need to replace the SXT AC for scanning, putting back the 5HPacD after doing the spectral-history.

Once you have determined the best frequency range you can start setting/tuning your link.

Ok, so I've updated my ROS and there seemed to be an improvement with CCQ hovering on the mid-80's to low-90's (and Tx/Rx of around -55). I've begun playing with the transmit power on each end and they are currently set to 12; however, I'm not seeing a big difference in CCQ over the "default" setting. I can't really replace the AC's with a regular SXT's for a spectral scan as I don't have any to replace them with (and no dept. budget to buy a set just for testing). Checking the traffic tab for the wireless interface I'm getting zero drops and zero errors and a transfer rate that maxes out around 95Mbps. I feel like there's something I'm missing here that's holding back my transfer speeds and connection quality and as PtP wireless is new to me I'm not sure what that is. Thanks for all the suggestions and if you have anymore feel free to share.

Don't you have any non-AC mikrotik radio, or any brand 5GHz radio to do the spectral analysis at each end?

At the very least try a Frequency scan to try to determine how's the spectrum there, the first thing to start with is an optimal channel selection.

choose supperchanel under advanced set scan-list to wide frequencies range like 5000-6000

and do /in wire frequency-monitor number=0

and in wire scan number=0

find best frequencies without inference

I've been backed up with helpdesk so far this week but I will be coming in early tomorrow to attempt to scan the spectrum. The only 5Ghz device I have is my laptop - will running inSSIDer be sufficient to give me a good idea of the frequencies in use in the area?

Try what kristaps suggested that will be enough to find the best channel/free contiguous area in the spectrum...