From the description of events, it sounds like the horse found trailering stressful right from the start. You describe the horse as sweating in the trailer. Each of the following trailering events may have further convinced the horse that it did not like the trailer. The final trailering incident, where you tried to get the horse into the trailer with a rope, may have even acted as a punisher in the horse's mind. "Approach the trailer and bad things happen." So, I would start over.

Here are my suggestions for starting over - first, you could pick up a John Lyons book that addresses this subject. Check Amazon for used copies- they are usually cheaper. Or, you could use the modified clicker training version with a faux trailer that I've described below. Or you could check my thread in the training log under "neglected Arabian mare," to see how I trained my mare to trailer load. One of these suggestions might provide ideas.

If you use the suggestions below plan on at least 5-10 training sessions of 20-30 minutes each.

In general, the horse needs to be reinforced for choosing to enter enclosed spaces. You will make this the horse's choice, but you will influence the choice by delivering a reward for certain actions and not others. The reward you use must be something that the horse really likes - usually a treat like bits of apple or handfuls of Senior feed work well. If you don't have a trailer, you can make a similarly enclosed space out of straw bales, a tarp, and sturdy plywood.

Begin with a plywood sheet (this will act as the floor of the trailer). Lead the horse up to it. DO NOT pull the horse towards it at any point.

Anytime the horse looks at the plywood, sniffs it or steps on it is a reinforceable moment and you must give the horse a treat at that moment. Be generous with your treats.

Next, you should step onto the plywood. If the horse follows give it a treat. If the horse does not step onto the plywood, lure the horse onto the plywood by holding out a treat or tossing a treat onto the plywood.

As the horse places a foot on the plywood, give the horse a treat. Second foot = another treat. Third foot = another treat. And so forth. Put a big pile of treats on the far side of the plywood. Once the horse crosses the plywood, let it eat the "jackpot" of treats. This helps teach the horse that crossing the plywood makes really good things happen.

Once the horse is walking across the plywood, put up the first wall. This can be a stack of straw bales stacked high enough that the horse cannot see over them. Repeat all of the previous steps.

Next, put the second wall of straw up about 10 feet from the edge of the plywood so you have a wide area to walk through. Repeat the previous steps.

Gradually move the wall of straw closer, until the horse is walking between two walls that are the width of a horse trailer.

Now, lead the horse onto the plywood, stop, give the horse a treat, and back the horse out.

Gradually increase the amount of time that you stop on the plywood to 1 minute. Then, back the horse out.

Next, put a tarp over the top at a height of about 8-9 feet. Repeat the previous steps beginning with leading the horse up to the "trailer," reinforcing the horse for passing through the "trailer", reinforcing the horse for stopping in the "trailer" and backing out.

Finally, put a 4 foot high stack of straw or sheet of plywood on it's side, across the end of the plywood "trailer" leaving the top half open. Lead the horse into the trailer and immediately back him out. Gradually increase the amount of time that the horse stands in the trailer before you back him out.

Last step is closing the end of the trailer completely with a stack of straw or a sheet or two of plywood. Repeat the previous steps.

Good luck.