Im sorry the correct reference is Exodus 21:10 not numbers where Moses states if a man takes another wife is not to neglect the first wife. You need to do a little research into Corinthians and the issues Paul was addressing. Those folks were into all kinds of things including homosexuality that is clearly a serious sins.
In essence what you are saying is that only certain Mosaic laws applied and others didnt. I didnt know we could pick the ones we like and abolish the ones we dont. Jesus said not one letter of the law would pass away.
You must remember Paul had previously been a Pharisee and been educated in the Jewish laws and customs and it shows in many of his letters. Paul also said all things are permissible but not all things are profitable now shall we take that out of context and run with it.
I think the issue regarding polygamy needs to be dropped, it could well give someone the idea that it is an acceptable life style, in certain countries it still is. Here in the US it is against the law and Jesus said we are to submit to those in authority over us. So from that stand point it is wrong, and the very least a very bad idea.
As for those seeking full time ministry, I think they at least should have a good biblical education, come into the ministry under a pastor of a good bible teaching church and remain there for some time. There are so many pitfalls a young or inexperienced pastor can fall into without proper guidance.
We can split hairs over doctrinal or theological issues forever and that is one of the things that have caused so much division within the body of Christ. I still like what Wesley said Love the lord your God with all your heart, and love others as yourself, all the rest is just commentary
As for colleges, there are some very good ones, I think Liberty is one of my favorites now.