I agree that you need to do a little research on grape pruning and training. They can be very vigorous and get out of hand if not pruned properly. "Over pruning" them will not cause permanent damage, but can lead to zero fruit if all the fruiting buds are cut off (fruit buds are on 1-year old wood). I tend to agree with desertdance that it sounds like you now have two 1-year old shoots that should fruit well this year (a picture would really help). The real question is what kind of grape vine is it and it is worth messing with? Why bother if the fruit is not good - replace it with a known variety and harvest good fruit.

You should be pruning in late winter and you must leave some of last years wood in order to get fruit. If you prune off all of last years wood, you will get nothing. You can tell the difference between one yr and older wood by the color of the bark.

Re your trellis: Eventually, you'll have to add heavier verticals to support the structure. Horizontals can be fairly lightweight. The vertical supports have to be very substantial, however. Commercial growers use steel wire for the horizontals, but use heavy anchored posts for the vertical supports. Think along those lines. There are many. many 'systems' to train a grapevine to a trellis or other structure. One 'system' might work best for a particular variety and another system might work better for a different variety. Grapes are very adaptable, however. As long as the vines are getting enough sun and they are pruned correctly in the spring, you can usually adapt them to just about any structure that is strong enough to support them. Good luck with your grapes.

I think the best time to prune in areas with freeze danger is in spring just before or as growth begins. I think this is too early in zone 7. I'd take cuttings for rooting 2-4 weeks before growth begins. Then they may need to be buried or stored in a cool place until rooting. It depends on whether you can control temperature or are reliant on nature, they need warmth to root rapidly. I'm not an expert on rooting grapes but have done it many times. Usually by just planting them where I wanted a vine, covering until spring, and then uncovering the top bud. This works but there are ways that result in much higher % takes. The key to rooting them is getting callus formation first. This works best at warm temperature, just the right moisture level, and rooting hormone. The cutting needs to be fully turgid but not wet. Some experts callus them in moist sand. This months Good Fruit Grower has an article on rooting grape cuttings. I've never used rooting hormone so that's not essential.