What is the religious ruling regarding a committed, bearded young man who intentionally does not pray Fajr and refuses to be woken for it, and would he be a suitable husband if he continues in that state?

What you mentioned about your husband regarding his commitment, piety, and his feeling of guilt for delaying the Fajr prayer is an indication of his good character. Perhaps Satan has whispered to him, for Satan may try to make a person oversleep to cause them to miss the night vigil (Qiyam al-Layl) and the Fajr prayer. The proof for this is the Prophet's (peace be upon him) saying: "That is a man in whose ears Satan has urinated," and the Hadith: "Satan ties three knots at the back of the head of each of you when he sleeps..."

As for his refusal to be woken for prayer, this casts doubt on his uprightness, and it is not possible to definitively assert his righteousness or lack thereof.

If the marriage contract has been concluded, then you should continuously advise him, supplicate for him, and be patient. If the contract has not been concluded, it is safer to be certain and not rush into marrying him.