The bioavailabilty of morphine orally varies a bit, and so does the metabolization of codeine between, so I can't say what is equal to what for you, but generally morphine is roughly 6 x more potent orally than codeine. 20 mg morphine doesn't seem like it would be too much, but you don't take much codeine at all, so I'd start with just half a tablet of morphine, 10 mg. I don't know if you have tolerance to benzos, but if not, I'd just start with the morphine without the diazepam. You are used to opiates, and are dependent apparently, so I don't see real risk in taking oral morphine for some stress. If the morphine works well at 10 mg, great. If you want to be a little more sedated maybe add 5 mg diazepam to that for your next dose. If the morphine just doesn't cover it at 10 mg, try 15 mg. If that feels right, but you still want some added sedation, again I'd add maybe 5 mg diazepam. If you have to go up to 20 mg, fine, you can take 5 mg diazepam with that to. But, without a benzo tolerance, I wouldn't add much more than 5 mg diazepam, 10 mg tops probably. I'd start experimenting with the morphine before whipping together opiate-benzo cocktails. You know opiates well, even though you don't take much, so you will know what amount of morphine is right. When you find that dose, stick with it, and as I said add a smidge of diazepam if needed.
Also, if you do end up using the diazepam more, take it before the morphine, so that the diazepam doesn't bring you down at all from the morphine. Just go slow, and get to a cushy spot. Also, a warning benzos are extremely addictive, and benzo wd can be potentially fatal if you come off of them after having taken them for a while. Most addicts who have gone through both opiate and benzo wd agree that benzo wd is by far worse. I am very sorry for your loss, I hope the opiates and benzos help you. They can truly work wonders. Again, beware of benzo addiction, and jacking up your opiate tolerance too much and creating a much larger habit.
