My dipladenia suffered through one 32 degree light frost. We brought them inside within a few hours; leaves dried up but soil not frozen. If we remove all dead leaves and cut back stems, will it regenerate in a 70 degree environment in a southwest window?
It won't hurt to try. You can check for stem damage by scraping off some of the stem. If it is green below, the stem survived, but if not, trim till you reach green stem. If needed, you can cut it all the way back to about 6 inches. Water sparingly for the winter and hopefully, you will see some new growth (may not regrow till spring).
https://www.gardeningknowhow.com/ornamental/vines/mandevilla/growing-a-dipladenia.htm
It also shares a pot with wild violas that I have to keep pulling out as they run wild
Unfortunately, your photos did not come through. I am unable to see the pest in question. What I can do, in the meantime, these articles will help you to craft your own pest control solutions:
https://www.gardeningknowhow.com/plant-problems/pests/pesticides
As long as you repotted it correctly, and carefully, it should be just fine.
https://www.gardeningknowhow.com/ornamental/vines/mandevilla/growing-a-dipladenia.htm
https://www.gardeningknowhow.com/ornamental/vines/mandevilla/repotting-mandevilla-plants.htm
What do I do for winter? Can I dig it up and repot?
I would keep it in a container instead of planting and digging up every year. This can get rough on the plant. This article will help:
https://www.gardeningknowhow.com/ornamental/vines/mandevilla/growing-a-dipladenia.htm
it indoors Sun room does not freeze but it does get cold in our zone 4 winters. So maybe I should bring it indoors in the house.
Dipladenia does best with constant warm temperatures so inside the house might be better than the sunroom. You can cut it back to about 8 to 12 inches before bringing it in. Check it for insects. You may want to spray it with Neem oil just in case. Don't worry if it doesn't bloom, you just want to get it through the winter till you can put it back outside in spring. Withhold fertilizer during the winter and water just enough to keep it going.
https://www.gardeningknowhow.com/ornamental/vines/mandevilla/growing-a-dipladenia.htm
It is being kept inside for winter.
Aphids can be a bit annoying, but they can be controlled. My go-to is azadirachtin. This is the concentrated active ingredient in neem oil that makes it effective.
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/azadirachtin-vs-neem-oil.htm
https://www.gardeningknowhow.com/plant-problems/pests/insects/homemade-aphid-control.htm
Just read your article about the best hanging plants and wanted to add one: Dipladenia. This is my go to plant as it blooms and blooms all summer until the frost. The Hummingbirds love it as well. I usually have 6 or 7 of them each year.