Is it right submitting a site to 2 appropriate categories? How do I suggest updates?

1) One of my clients is in business of manufacturing Pharmaceutical Machineries, Lab and R&D equipments etc. One of his competitior's website http://www.cadmach.com/ has been listed under category:

http://dmoz.org/Regional/Asia/India/Business_and_Economy/Industrial/Manufacturing/Machinery_and_Tools/

Is it the correct category to get another site engaged in similar business?
(I read in one of the threads "Some hints: look at the sites that are already listed in the category that you are considering, to see if they are similar to yours in topic; conversely, if you know of other sites that are similar to yours in topic, see in which categories they are listed."

2) As the client is manufacturer and exporter and having Clientele worldwide, I found the below mentioned to be more appropriate category:
http://dmoz.org/Business/Biotechnology_and_Pharmaceuticals/Pharmaceuticals/Tools_and_Equipment/

I found http://www.umangpharmatech.com/ another competitor's website to be listed under the later category. The Hint again applies here, can you help me?

3) May I go for both? I know that would be more like spamming, if I submit a site more than once.

4) If a site gets listed. How do I suggest any changes in listing if a site contents are updated/changed?

A site can have more than one listing in a situation like this. The regional/ listing is for the sites with a relevance to that geographical area-for example the location of their physical presence. The topical category is for the type of product or service they offer.

There is nothing wrong with having several sites listed in the same category on the same subject (i.e competitors) so long as they are all relevant to the category and each in on its own is listable, they are not affiliated sites of each other, and each has unique content to offer to the category.

Suggesting the site once to the single best topical category and suggesting it one time to the single best Regional category would not make you a spammer. Multiple suggestions and resuggestions to the same category or multiple categories would be spamming.

There is an "Update Listing" feature at the top of the category for suggesting changes to a listed site. This would include dead links, listing errors, url changes, and major changes in content.

Hope that helps.