[MD] Healthcare reimbursement vs. deduction in my severance pay

Background: For the last 10 yrs. I’ve managed a private practice office. 830-430 M-F, 13 days off, 401k, $25/month towards cell and $300/mon. for healthcare. Never used all my days off, dedicated, boss never needed to check in when he was away. Small office – boss, his accountant, myself, an assistant then a few providers. Got written up 1st time in Jan ‘25 for being late a couple times (with reasoning, whatever). July ‘24-July ‘25, I struggled with some depression dealing with awful roommates which I expressed & just wasn’t as proactive at work.

Things improved, asked for a larger than usual raise in June (I usually get 5%, asked 10-12%) since I hadn’t had a “review” for 1.5 yrs & was hitting a milestone – but it kicked off the accountant (who’s never liked me all that much & been 100% virtual traveling for yrs so she’s out of touch with the physical office vibe) wanting me to provide work logs, delegate tasks I’ve always done to my assistant. Mind you, I've never had a formal written review my entire time I've worked there. Things seemed weird, I could feel it. Boss wasn’t being straight forward, dragged my request, 3 months later offers a 6% raise and asks to schedule another meeting in 2 months. 1 month later, after hours he happened to see some uncashed checks I opened and left in the corner my desk stack, something he’s done & myself plenty. The office is locked, we do have cleaning people, but it was completely blown out of proportion. Acted like I was trying to bring the company down. He writes me up a 2^(nd) time, asking me to write an SOP regarding check procedure, and that it could put me in jeopardy. I feel like he’s just trying to push me out with the accountant on his shoulder.

Did that and not even a week later, I’m being asked to resign “because he just can’t get over it” but so I can leave on good terms, rec. letter, he offered 6 weeks of severance with “full pay and benefits” to find a new job. I explained I hadn’t even been given a 3^(rd) strike and I was under the impression I was doing my duties, but apparently it wasn’t enough, which was never clearly conveyed or put in writing. 10 years reduced to like a 10 min conversation, he had a one-line resignation letter typed up, I signed it and left.

Checking my final direct deposits and I realize my $150 per check for healthcare isn’t included. Apparently because my healthcare stipend had to be provided as a reimbursement instead of a deduction, it’s not an “employee benefit”. This is no fault of my own, they didn’t tell me my plan changed this year until it was too late and had to get private ins. & pay on my own. I questioned him since he SAID “benefits” - he agreed the accountant was right but that he would offer a $300 one time addtl payment which I got. But he still owes the last $300. I have one more check coming for a week of pay and 6 days I didn’t take off. I shouldn’t have to feel bad about asking for the last $300 I should be owed for healthcare as part of my severance.

TL;DR How can I express without being demanding to my former boss that he NEEDS to add $300 of the last “benefits” I’m owed to my check since he said he would when I left - before my last severance check gets processed. I wasn’t told my healthcare reimbursement wouldn’t be part of severance; that’s on them. The amount isn’t a lot and after 10 years, it’s like come on!

Even though I was asked to resign, I’m still going to try to file for unemployment as soon as that last check gets processed, regardless if I get that last $300 or not.