I read chewing damage might be due weevil insects. Nematodes are recommended to put on the soil to go after them. Can you tell if there is anything else I could do? Or if my assumption is correct?

My goal is to obviously get it as healthy as possible, and promote branches since I want the round dense shape.

I will greatly appreciate advice.
Thanks

Weevils leave sharp notches along outside edges of leaves. Nematodes applied in Fall can be effective for the larvae (in ground and feeding on roots) - you can hand pick the adults that are feeding on foliage. There are sticky barriers you could apply to plant base, chemicals that could be sprayed to kill adults but for some cosmetic damage on one or two plants, I wouldn't go to the expense.
Go out at night after dark with a flashlight - if you do have weevils you'll find them (climb somewhat slowly so you may not find them right at dusk). If you don't have weevils but something else like climbing cutworm that damage rhododendron here, you will have identified the pest and can take the correct action.

I'm seeing one dead branch, that could be either rhododendron borer (see link), or drought. Sometimes rhododendrons will respond to drought by having individual branches die leaving others unaffected.

To encourage a rhododendron to grow to a more compact full shape, wait until Spring when blooming and pinch out new foliage buds with your fingers as they are starting to elongate and unfurl. (flower buds are blunt/fat, foliage buds more narrow and pointed) Removing the foliage buds will encourage dormant buds positioned lower to begin to grow...repeat for about three years until you have the more dense form you desire.

The other damage looks the same as your Purpureum.