Sorry to hear it's not doing well.

I'm just a casual hobbyist but here are my thoughts...

I would not give it any fertilizer at this time.

I think it is ok to trim off any branches that are *definitely* dead--brown and crispy inside--but if anything looks like it is still green leave it alone--it can be misleading sometimes from just looking at the bark, check carefully. It didn't get any freeze damage right?

How's the water situation?--make sure it is getting enough but not staying soggy. How long ago did you replant it? If it's recent you may see more changes; if it's been a while maybe it can turn the corner if you're careful with the water.

HTH.

Meyer is the most nit-pinicky plant I know. I have 3 meyers and I have the same problem before. They are now looking very healthy.
If I were you, that is if I were you I would dig that meyer and plant it again in a pot the same size as when you have it.
Right now it is in shock and it may go if you are not careful. I think that being in a pot you can take care of it better. You can regulate the temperature for one thing and the pH of the soil.
Dig it so you don't bother the roots at all. At this time it may have root rot by now. You said you damaged the roots while transplanting. You should have cut the branches off in proportion with the damage roots because one of the reasons you lost most of its leaves is because the roots can not sustain the leaves demands for water/nutrients because of the roots ' removal. It is not too late for you to trim more of the branches even when they are green.
You will see they will bounce back with very green new buds once the tempt goes up. Don't believe the other's that you'll hurt the tree. Don't be afraid to cut the leaves and leave just a few.
Second don't give any any fertilizer this time. The roots is not ready to take in fertilizer because it is still in shock. The less fertilizer it consumes the better it is.
The first time you transferred it to a pot drenched the pot wiith lots of water. You want the salts and the fertilizers out of the soil at this time. Run a trckling water to the pot maybe 20 minutes until you can be sure all the salts are gone.
Then put a transparent plastic cover over the plants and create a 3 to 4 holes as big as quarters on top.
Now put it on the window sill but not in direct sunliight for about 5 days. Or until you see new buds are coming out. Then that is the time you can fertilize at 1/4 the dose. Use the miracid by Miracle grow fertilizer at 30-10-10 use for azealia/rhoddendrum/ camelia fertiler . Don't water it anymore until the 1st 2 inches of soil is dry. It is better to trim the tops right now to better serve the leaves by the remaining roots.Make sure the soil is every fast draining. A good mix is 1/3 sand 1/3 peat 1/3 top soil.
I hope you don't have root rot at this time. Check it first. If your roots is still healthy I am sure your tree will recover.
Treat it just like a sick child. Only clear liquids, no solids and rest. Lots of it.

I also think you should put it back in the pot. When I lived in Dallas I had one in a pot that did fine. They won't survive the winters in Dallas...so if it's in a pot you can move it into the garage next winter when it gets cold. I would use Miracle Grow potting soil to help it out, and for now I would keep it out of that brutal Texas afternoon sun. Morning sun for now...baby it! If worse comes to worse, you could try to propagate it...I've done that with a couple of plants that had sentimental value...just in case. Also, North Haven Gardens in Dallas is a great nursery...they might be able to give you advise.

I have heard from the "experts" here that miracle grow potting soil is one of the worst soil you could use because it holds too much water and compacted in less than 2 years time so you'll have problem on watering.

Once inside make sure you flush it in the tub. Run a humidifier every few days, mist sometimes.Indoor air can be so dry it will make them dissatisfied with the sorroundings and will show you. After you do all this after a few weeks, you will see new growth next.

Many thanks to you all for the advice! I didn't say this before, but the tree has been in the ground since early/mid-January (so, 2.5-3 months).We had an extremely mild winter, but there were a few days of below-freezing temperatures. I did wrap the tree a little, but I can't imagine that it helped. So I guess it could also have freeze damage.
How can I recognize root rot? And if it has it, is there anything to be done?
Also, how do I know how much to water it? The ground here seems to dry out quickly, and we have had very little rain.
I never thought about repotting it; that does sound like a good idea. Especially since I'll eventually be moving again! I'm definitely going to get in touch with North Haven Gardens, too.
Thanks again.

Pop, if you'll be moving again, I'd definatly keep potted. If you place it in the ground, and keep moving, eventually the tree will die. At least in a container, it won't have to be dug up each time you move..Only when you're sure you'll be living in the same place for years to come should you plant in the ground.
I would remove dead branches, but make sure they're really dead..you can wait a while to see if any new growth spurts. Or carefully shave a piece of bark..if you see green then that branch is alive, if it's brown then it's dead. Any branch that is flexible when bending is alive. if it break off than it's a goner.
I don't know what to tell you about fertilizing..Most professionals insist a sick/stressed/insect plant should not be fed.
If you do repot in a contaier there won't be any need for fertilzer because fresh soil contains nutrients. Keep us posted..Toni