Have you seen other trees of grapefruit in your area? I'd expect it to freeze in bad winters. A lower, wider tree would be easier to protect.
Do you know the variety of grapefruit or the type of rootstock?
Jessejean, citrus don't require pruning unless branches are way out of proportion to the rest of the plant or branches are rubbing against each other. You didn't mention how big the tree is at this point. I'm assuming it is still fairly small. In that case, leave it alone. The more leaves the tree has, the more it will be able to photosynthize and grow. Did you purchase a dwarf or is yours a standard sized tree?
The tree is a Rio Red dwarf. I got the tre from a well known vendor in Texas. It now has two main sections, one full of blooms and the other just leaves. They look very healthy. I want to pant it in the ground . SHOULD i GIVE IT ANOTHER YEAR IN THE POT?
EDIT; THIS IS A NEW TREE. Not the one mentioned above. Although the original one is still alive but not showing any encouraging signs.
You will need to find a warm microclimate part of your yard. Grapefruit produce the best tasting fruit in places with warm summers. Here's a link to Four Wind Growers, my favorite nursery when I lived in California, that explains reasons for it. http://www.fourwindsgrowers.com/solver/heat.html
Go ahead and plant it. It will get bigger in the ground. You mentioned the tree has two branches, one is blooming and the other is not. Are you able to post a photo showing the area around the graft union? It is possible the non-flowering branch comes from below the graft. In which case, you need to cut it off. Branches growing from the rootstock will be more vigorous, and eventually kill the grafted portion of the tree. If the non-flowering branch comes from above the graft union, leave it. It will help provide nutrients to the tree. In a year or two, if you prefer a single trunked specimen, you can one of these branches off.
Where has your other tree been planted? Citrus like rich, moist, well draining soil. Your soil is likely very sandy. What is the salt content of the soil? Citrus are given citrus fertilizer according to the trunk diameter. This amount is then divided into 3 or 4 feedings a year. In sandy soil, you may have to feed more often. Another thing to remember is, citrus grow in spurts. Try to time the feeding so the tree receives the fertilizer shortly before a growth spurt. Plant citrus at the same level as they were growing in the container they came in. So don't make the planting hole any deeper than that.