Hello Laurie,
Sounds like your mare has been through the wringer. Many of your questions don’t have firm answers, particularly considering individual variation. However, as to whether to mix or just increase the dose of the Equioxx, more is known about using single NSAIDs as opposed to combining them. There is the issue that it takes longer for the Equioxx to get to a steady state but here I would err on the side of safety. The article discusses long-term studies of Equioxx and increased doses. It suggests you are unlikely to experience problems at the doses you are using. How long should you continue? You should reduce dosages as quickly as possible in response to improving pain and inflammation. I would suggest support bandaging for the continued swelling.
DrO
PS sorry for the delay we have been traveling out of internet range.