^Good post man. You covered it well.
If you only IV once per day, using the same vein is not HORRIBLE, but certainly not ideal. Try and move up and down that vein, though, if it really is the only one you can use. Start further away from your heart, and move closer with each injection.
Vitamin E cream is great for promoting healing. Make sure you use the smallest gauge needle you can find, ideally 31g.
There are a bunch of vein maps available on here, and using google you can find them as well. Just because you cannot see the veins bulging out, does not mean there are no usable veins. You should invest in a tourniquet and spend some time trying to find some other locations to use, because that vein will not last forever. What will you do then ?