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It sounds like he may have "pollarded" the tree. Crepe myrtles can recover from this type of pruning, but may look a little odd for a few years. The tree should start rebranching and should bloom again in 1-2 years.

I suspect the trees have Cercospora leaf spot. In some varieties of crape myrtles, the leaves will turn red. It is increasing problem for trees in the South. This article should help you:
https://www.gardeningknowhow.com/ornamental/trees/crepe-myrtle/crepe-myrtle-tree-problems.htm
https://www.gardeningknowhow.com/plant-problems/disease/cercospora-leaf-spot.htm

This seems to be a common question; yet, it is one in which many of the experts (myself included) simply remain puzzled about. Most people believe that the color change is based on the pH level or acidity of the soil they're planted in, much like hydrangeas. I, too, would point in that direction. However, the majority of experts disagree and claim there is no scientific proof of this.

Instead, it is believed that this phenomena occurs as a result of two different seedlings having been planted together, or one grafted onto another. Another possibility may be linked to genetic abnormalities.

This is typically a sign that the plant has too little water. This article outlines how this can happen:
https://www.gardeningknowhow.com/plant-problems/environmental/what-causes-brown-edges-on-leaves-of-plant.htm

Trees will put out suckers when they are stressed. Some trees, like grafted trees, are always under a little stress and will always put out some suckers. You can reduce the number of suckers a tree puts out be removing stress from the tree. Make sure it is well watered and fed and that there are no pests affecting the tree. To control suckers popping up away from the tree, you can cut the suckers as they come up and paint the fresh cuts with Round-up. It may take a few times but that will do it.

Here is more information: https://www.gardeningknowhow.com/ornamental/trees/tgen/tree-sucker-removal-and-tree-sucker-control.htm

Yes, you can cut the flowers off. This will not harm the tree.