Yes, yes and yes.
Generally speaking, there is no advantage of using colloidal silver topically over ionic silver when it comes to topical applications. In fact, ionic silver is felt to be superior by many when it comes to topical applications. One caution would be to make sure that you are using an uncontaminated silver solution, especially one that is uncontaminated by salt. Personally, I would also stay away from larger particle silver solutions if I were going to use DMSO and have the silver penetrate into the skin.
I have used silver topically scores and scores of times.
Herbal Healer 500 PPM silver? It is probably OK to use topically (though I would NEVER use it internally). I note that it is only 99.9 pure compared to the best products which are 99.99 pure and further note that 500 PPM is way too much silver to take orally in any quantity. Their claimed particle size is pretty small, though not nearly as small as the 0.65 nanometer particles found in Utopia Silver and Mesosilver true colloidal silver solutions. I am pretty sure that their product also contains some form of protein, perhaps animal protein, because you cannot suspend much more than 20 PPM silver without it agglomerating and precipitating out unless you suspend it in a medium that is not pure water.
Topical silver is best when you can keep it moist and in contact with the area being treated. I have poured it on, put it on with Q-tips, rubbed it on with my finger, used a 50 PPM silver/aloe gel product I like a lot, and put a cloth/guaze type bandage on and kept it wet with solution. The latter is probably the best. I have also used many, many of the silver skin and scalp bars from Utopia Silver. They are good to bathe with, shampoo with and even use to brush your teeth with (say goodbye to plaque and gum disease).