Donor angst

Dana • We have one amazing 5yo IVF baby. 41 and TTC #2. After 4 retrievals with 6 failed transfers, we're doing a few Hail Mary IUIs in Feb/March to use up our donor sperm, then closing the book on TTC 🤞
My wife and I have been talking about starting a family for years, and we were so happy when my brother-in-law offered to be a sperm donor. It seemed like the perfect solution - we know and trust him, and better yet, although he'd always be an uncle rather than a parent, our child would grow up knowing who their biological father was. Ideal. 
We naïvely assumed that, since he has 3 beautiful children of his own, there would be no problem with his sperm analysis. This week the results came back showing high MAR (antisperm) antibodies :( We now have to decide if we try IUI despite the reduced chance of success (and therefore, more expensive and disappointing IUI cycles), or look for an unknown donor. So emotional about the whole thing, I'm just a ball of angst!