No, carrying hand weights is not a bad idea. It is a good idea, despite the naysayers. I'm on day 651 of my running streak. (1 mile or more every day, no stopping, no breaks, no excuses, no exceptions. www.runeveryday.com
I frequently run with two 15 pound dumbbells, sometimes with two 8 pound dumbbells. It's a lot. You might consider using less. Today I will run 3 miles with 30 pounds in hand weights.
It has had a profoundly beneficial effect on my cardiovascular health and endurance, and I am not just talking about endurance while running, if you catch my drift.
In my twenties and thirties, I ran faster, but could not run everyday. Running gave me knee troubles. But now, in my fifties, I have no trouble at all with it, even with the weight, perhaps because of the weight.
It tends to hunch me over as I run. It's not permanent. Some might object to that. For me, the previously mentioned benefits outweigh looking hunched while running.
Ankle weights on the other hand, have caused me trouble. I believe the additional cyclic reversed loading stretches the knee ligaments, increasing the shock loading on the cartilage during footfall, and reducing the lateral stability of the knee joint. I only ever use ankle weights for floor exercising. I am very intentional never to laterally load my knees, and load them only in their axis of rotation.
There is much misinformation about this topic, even by professional coaches.
That said, if your goal is to tone your arms and shoulders, there are probably more efficient ways.
Keep on trucking. Do what you can, and then try to add 0.01 more.