Well the Eastern Rite Catholics (Middle East) can in fact marry. As for your other excellent questions, let’s see if others have inputs. God bless.
The Church in the West had to wage a protracted struggle against secular power. Bishops and abbots owned estates, whose income constituted the main support of the Church, but as owners of land in the realm, there were constantly pressured to become mere vassals to the king and way too enmeshed with the political nobility. (Look up Investiture Controversy and you will see that reforming popes struggled AGAINST this for centuries.)
If a bishop had sons and daughters, hed be even more deeply caught up in dynastic marriage politics: marrying this daughter to that duke, and this son to that princess, and forming alliances with powerful families for all the political/economic/social benefits that would accrue.
Trying to secure the independence of bishops from the temporal Powers-That-Be was a huge job. It took a millennium to settle and its not what Id call settled even yet. But, for many centuries in the history of the Church, marriages would have forced priests and, even more so, bishops and abbots, to become even more deeply enmeshed in securing titles of nobility, access to estates and lands, royal alliances and the rest of it for all their children.
The Church was trying to steer clear of that whole web of worldly entanglements. Celibacy --- the avoidance of ongoing dynastic interconnections --- was THE honorable way to secure independence from worldly preoccupations and temporal power, and hence more freedom to be "in this world but not of it."
This has --- I should say primarily --- the value of "eschatological witness," which means they were dramatically demonstrating that they expected to receive full recompense by having the entire Christian community as their family in this world, and eternal life in the next. Check out Mark 10:28-30 (Link).
It was (and is) the most powerful of motivations to be able to follow the example of St.Paul and of Jesus Himself, in trading earthly for heavenly priorities.
Sometimes people wrongly think of deacons as laymen, but this is incorrect. Deacons receive the Sacrament of Holy Orders and are clergy under the Bishop, not just added-value laymen assisting the pastor.
Our deacons --- and their wives --- are real treasures. I can hardly imagine how the parish could function without them.