Okay - I assume the 2 to 6 refers to morphology on the Kruger (strict) scale, where >14% normal forms are the "ideal." Anything below 5 is classified as male factor infertility, and below 10% is considered "subfertile." 10%-14% is borderline, but they don't usually see reduced fertility from that alone. The good/interesting thing . . . morphology is one of the easiest things to fix with vitamins/diet/lifestyle changes! Also, varicoceles can have a big impact on morphology, so correcting any varicoceles can greatly improve the morphology.
Staying away from caffeine/heat/baths is important. Vitamin C (1000 mg a day) is shown to greatly improve sperm morphology, and I've read a lot about pycnogenol helping as well (it did improve for my DH after we added pycnogenol to his supplements). Vitamin E is also good for morphology. Those are the key ones . . . some people say L-Arginine and L-Carnitine help, too - depends on how many vitamins your DH is willing to take. Mine has been taking a bazillion, but it really has made a big difference.
GL!! Male factor does make it much more difficult to get pregnant, and it is more frustrating that female infertility because you can't just take medicine and make it go away, but it can happen even if you don't improve the morphology. We had a big motility problem, and the waiting was killing me. The good news is, if you have to turn to IVF down the road, MFI has one of the highest success rates with IVF. Hopefully, you can improve his morphology and get your

without additional help!