You don't have to hold the skin tented up. You just do it initially to make sure to get the needle into the right place between the skin and muscle. As for administering too fast, you would need to ask your vet about that, but it sounds like you did a good job getting the fluids administered. GI blockage is when the digestive process stops or nearly stops. If she is still pooping some then she doesn't have a blockage. She has slow gastric motility, which if it continues to slow down from lack of eating sufficient amounts, could eventually develop into a blockage.