Site Merge / Backlink ?

Hi there,

We have an old domain (20 years registered) that, about 5 years ago, was merged into our primary website using a 301 redirect. This was done simply to consolidate. The backlink profile for this domain appears to have approximately 200 or so links. Upon further research, the majority come from three directories. These directories have decent authority, and upon using various tools to check for spam, they appear to show nothing too alarming.

However, after looking at the actual citations, I've noticed the links to the old domain use keywords, which can appear to be "spammy".

I attempted to contact the directory companies, but they are either so old that they appear to be no longer managed, or they were abandoned. With this said, I have no way to request an update or removal.

My question... Based on the above details of the domain's backlink profile, do you feel it would be best to undo the merge by removing the 301 redirects on the .htaccess of the old domain, or add the old domain to my Google Search Console and disavow the potential spammy backlinks? Additionally, I'm not sure if this matters either way, but the domain name in question is keyphrase-heavy as well. It has a domain authority of 11. Our primary website's authority is 25.

I am simply looking for the safest way to approach this. Our main concern is the health of our primary company’s website. I’m leaning towards just breaking the .htaccess redirects, but want to make sure that is the proper way to undo a merge if this is the best direction to go.

Any suggestions would be greatly appreciated. Thanks so much.