I feel like you are missing much of what I've said (several times) in this thread...
Well, I feel you seem to be missing is the fact that networks (both local and wide area - internet) run on numbers or IP addresses like "192.168.0.50" not names line "dlinkap". (and I'm surprised at this since you state you are an experienced network administrator) You will
NEVER be successful with http://dlinkap until you have
a correctly configured service (such as a DNS) <
NetBIOS name resolution> to translate the "dlinkap" to the IP address "192.168.0.50" [or what ever IP address you have assigned to your DAP-1522]
When you connect your mac laptop directly to the DAP-1522, do you know what service, on that single cable, point to point network, which is responsible to translate names to IP addresses? I don't believe there a service to fulfill that requirement, and
that is the reason that typing http://dlinkap in your browser does not work (and the additional possibility that the DAP-1552 may not be named "dlinkap")
When you connect your DAP-1522 to your router, the
router <
NetBIOS name resolution> is responsible for translating names to IP addresses. If the
router's DNS <
NetBIOS name resolution> is not configured correctly, there will be no resolution for "dlinkap" and the router will ask your ISPs DNS servers if there is any domain name "dlinkap.com" that can be translated to and IP address (your web browser is trying to 'help you out' in this failure situation by adding the .com to the end of your original request name of 'dlinkap'). Your IPSs DNS servers will find there is a domain "dlinkap.com" that can be translated to an IP address of 208.73.210.121 registered by Jan Svoboda (who has registered about 40K domain, definitely a squatter) and your web browser show you that page. [by the way, my employer has blocked my access to that site, claiming Filter Category: Viral_Content_Sites;Advertisements;Productivity - so be careful)
In each situation http://IPaddress does work, so this means the http://dlinkap issue is a result of name to IP address translation failure, not a failure with the DAP-1522.
If you can get past this issue, you may be able to get help for you other DAP-1522 issues. However, if you are frustrated with the setup and performance of the DAP-1522, perhaps it is not the best device for you. Stop driving yourself crazy, declare your unit defective, cut your losses (in money and time), chalk it up to experience, and go purchase another access point which may work better in your particular network situation.

EDITED: to replace incorrect DNS with NetBIOS name resolution