How is Concurrent Short-term Disability with Continuous FMLA affected by a Severance Agreement

I went on short-term disability for breast cancer the day before my employer terminated my entire department. Under the STD insurance, I can receive up to 12 weeks of income at a reduced rate (75%) and an additional 12 weeks at a further reduced rate (66 2/3) while maintaining all my employee benefits, including complementary gratis services and health benefits as long as I am eligible for STD under the STD insurance stipulations. However, the cost of these services would no longer be paid out of my paycheck, but I would have to mail them in each month.

They offered us a severance agreement ending all employee benefits at the end of the month but maintaining our health insurance under Cobra for three months at the employer-sponsored rate. During the 12 weeks of severance, I would receive a regular paycheck every two weeks, which would offset any STD payments during that time period. Before being separated I had an STD, a continuous FMLA, and an intermittent FMLA claim (all approved).

Before leaving the company the HR Partner confirmed with the Leave Manager, my situation was not uncommon, and I would still be eligible for my short-term disability insurance since it was approved prior to my termination date.

After separation, they canceled both FMLA claims after I asked if the 90 days of Cobra at the employer-sponsored rate would run concurrent with my STD claim or began after I had exhausted the STD claim. How does this affect my STD benefits besides offsetting STD payments for the first 12 weeks, because I will be receiving my regular pay every two weeks for a total of 12 weeks? And, does canceling my FMLA claims affect my benefits in any other way?