Dear cptmart,
You've asked some very pertinent and interesting questions. Unfortunately [or fortunately, in my view] only you can answer them. I will give you some stats though: in their rudimentary poll archives, TER established that about 50% of its users are married men. In addition, 43% of all Americans have some kind of sexual dysfunction; in men, it's usually related to erectile dysfunction or ejaculatory issues. Guess what it is in women - HSDD, i.e. Hypoactive Sexual Desire Disorder.
Now, there are many ways to interpret that last diagnosis. For feminists, they will simply state that our way of measuring sexual desire is modeled along the male libido [with some patriarchy thrown in for good measure.] For those who subscribe to some version of evolutionary psychology [yup, that would be yours truly], we see it as a biological issue and not a helluva lot that can be done about it, despite all the sex manuals and equality in this world. Men's and women's appetitive sexual desires are dissimilar, much because of the presence of so much more testosterone in males. As an example, I offer female-to-male transsexuals. Here are women who have been socialized as females, hearing all the moralistic propaganda against sexing it up too much, just like most people in America. And what happens when said females start administering T? They get horny as hell! They go from 0 to 60, if you get my drift. And it doesn't take a long time either. Within a few weeks, these males-in-becoming are jacking off, checking out women [or men if they are gay], and in general behaving like teenaged appropriately sexed boys.
So with all that, I can only tell you that if you expect your wife to get all hot and bothered and match your 28 year old male sex drive, keep looking. It ain't gonna happen, it's a biological impossibility. Now, having said that, does it mean that you can't have fun in the sack? Hell no, it just means it probably won't be as often as you may want it.
Which leads to your question if providers frown upon meeting married men. The answer is, in short, HELL NO! THEY DIG IT! What they don't want, is a married man to fall in love with them and become a pest. That will definitely compromise the provider-hobbyist boundaries. But married men are the bread and butter of the provider business, mostly because these guys get sick and tired of waiting around for next ovulation to happen in their wives. So you're totally safe in the married hobbyist role. Just provide the required screening information, answer honestly if the provider asks you if you're married [she may actually feel more safe if this is the case, it proves that you're not some delusional nut who's going to trail her around after the appointment is over], and enjoy your sexual experiences.
As to your next questions: This is something for you to work on, either by yourself or with your wife in therapy, should you be so disposed. Personally, [and I REALLY mean this PERSONALLY], I think it's absolute folly to get married before you're at least 35 and have sown your wild oats. Heck, at 28 you've only been out of college for 6 years at best, unless you're pursuing graduate studies. Do you seriously think that you're going to remain faithful to the same woman for the rest of your life? The stats are against you, no matter where you turn.
And yes, the men in the Bible had multiple wives...and some men in some cultures still do. But this is NOT the same thing, and let's not confuse visiting prostitutes with marrying two wives. If it were me, I'd stick with the providers and not even worry about the polygamous idea. Plus, I'm virulently anti-religious, so I don't really give a rat's ass about the Bible [sorry if I'm offending here, but I prefer to be brutally honest about such things.] Any references to various religious tracts, texts and orthodox traditions of any persuasion when it comes to sexuality will be met by my deepest contempt. There, now that's out!
You want to have my most hedonistic, Satanic, Black Sabbath-AC/DC-rocker advice: Fuck your brains out, whenever, with whomever, wherever. And do it sooner than later, lest the years tick away and you find yourself bitterly wanting to turn back the clock.
Back in Black On a Highway to Hell, for sure,
the Love Goddess