Retching, any insight or tips?

Take a video of what he does and pay attention to when it happens. Call the dr's office and ask if the doctor can view video and notes and evaluate what's going on/what can be done.

Hi Ohiogail, sorry I have no experience or suggestions but just wanted to say I’m sorry and wish your fil comfort and peace very soon.

Ask for anti-nausea suppositories. He probably has very sore throat.

Yes. My mother did. At the very end, she was retching up black bile.
If there is some way to elevate her head, it will be helpful. And if hospice provided swabs to clean out her mouth, try and use them...just be careful, because they caused my mom's bite reaction to kick in.
Prayers for you and mom, I am so sorry you have to go through this.

Any chance he's aspirating due to loss of the swallow reflex? I know during my mom's last several weeks she often seemed to be gagging on nothing, a couple of times she coughed/spit up huge amounts of phlegm.

I'm sorry you are having to go through this. Please keep asking the hospice nurse what else can be done for him, as there has to something else to give him, like maybe Lorazepam? I'm no Dr, but my husband died almost 5 months ago now under hospice care in our home, and his 6 week dying process was horrific. There were several times when I called the hospice pharmacy myself, to see what else could be done/given for my husband, so please don't be afraid to do that also. You are now your FIL's advocate, so make sure hospice is doing everything possible to make him more comfortable. That's their job!!! Praying for God's peace and comfort to be with you and your family, and that He will take him home soon.