@primrosechill I have considered IUI but we decided to give it a shot for a year with home insemination before going further with any medical interventions. There is a chance we will change our minds within that timeframe but at the moment we have too much non-TTC stuff going on in our lives, plus the pandemic of course! 😷
My GP has said that home insemination is only slightly less likely to result in pregnancy in any given cycle (due to some swimmers getting unavoidably damaged). In IUI though, they use "washed" sperm directly in the cervix, so you do get the best ones up there, very close to the tubes. The success rate is still not as high as intercourse, but it is decent nonetheless.
In terms of your husbands anxiety that bad sperm caused the miscarriage, yes, it is a possibility -it always is regardless of how the sperm got there. However, the thing to remember is that when you have intercourse or when you inseminate, the sperm is placed in the vaginal canal. It still needs to enter the cervix and travel all the way up to the tubes. And then it has to meet the egg and manage to penetrate it. If a non-optimal sperm managed to do that, it's not due to insemination, just bad luck I suppose.
Having said all that, there are no right and wrong answers here. If you both feel IUI is right for you, then I'd say go for it! 😉