Tbh. Its highly unlikely that you will face anything that disrupts business and can prove it being from this machine.

Even if you get hit by a trojan that encrypts everything: if you have AV on clients and servers and update their databases regularely, noone could or would blame a dude thats 3 months in the job for it. I mean you have no prior experience. Thats also why i would not try to escelate it further. You will get fucked by management if you fall in the back of a higher ranking position. They dont appreciate people calling stuff like this out. Especially in small family owned businesses. Trust me. I've been there.

You will most likely find even more hazards in the future. If it gets worse, make a list. If you can, put in the CVE Codes and their explanation about the issue and the potential risks.

Put it in a monthly report-email regarding IT Topics. Also put different stuff in there, so you dont only appear to be whining about the system that they obviously have been taking care of in a lackluster way. This way you show that you are doing your job for the case that there might actually be a hazard and if they ask, you can simply point to your monthly report and say you did your best and did not get enough ressources/coworkers/ or the so very much needed new Firewall Appliance.

In terms of futur vision: write up your daily systems you work with. I'll make some examples for your Resume:

• Config- and Patchmanagement of
• ~ 30 Windows 10 clients via WSUS and SCCM
• ~ 10 Windows Server 2019 Systems via WSUS
• ~ A Veeam/Synology/In-House Built Backup Solition
• Ubiquiti Firewall and AP Solitions
• Management of Microsoft SQL/Oracle/MariaDB Database Replications
• Management of an small scaled AD Environment with ~ 80 self created Objects
• GPO Policy Management
• Management of a Microsoft Exchange Sever Cluster
• ...

And so on.

Also make a second list with projects, what your role in them was (most likely project lead), and what situation you had and the target. Also in which timeframe you are working on it (March/2024 - Today)

Don't tell anybody that you are keeping your eyes out for a new job. Wait till you have landed a new job with administration work (dont do First-Layer Support Jobs. They get you stuck on your career ladder)

Also have a look at job portals like Kununu and check Ratings of companies. Since you are already in a kind of dispute with your boss I would suggest to not leave a review of your current workplace, whilst you still work there. Attention would be immediately brought to your end.

Also: if you are bad at creating a resume. Use an online builder. Job portals offer them. Be advised though, recruiters will already call the number that you type in there even before you are done typing your resume. rxResume is and FOSS Resume Builder. Can be selfhost or simply used by the Publicly hosted variant.