i understand you need suggestion to achieve your requirements , i would make movable object with transparent background and solid border to mark the spot a user want to locate , then upon click event on the needed spot a confirmation message should appear as well on this stage there is two scenario's you can do here
either you pop up a window form asking the user to insert details about the marked spot or you can set that @ the beginning during the map plane upload by dividing into static parts , when the marker object get into any spot of defined you can retrieve it's information through matching it with sliced part .
you can use phonegap technology to do that , it will help you speed up the work
beside that you can connect to remote db easily and there is already libraries on phone-gap can open /import auto cad files .
phonegap technology is platform created by adobe , it will allow you to make native mobile application for ios , android and windows , the great thing about it is you can use html / javascript on it ,after finishing the work the phonegap will generate the apk (ANDROID) , ipa (IOS) files for you as native application .
i searched using npm and i found like 5 plugs for auto cad which can read auto-cad files directly as dwg ...
click here to view it
here is adobe phone-gap official plugins library
click here to view it
even to make this more easier for you , you may use this platform development called alpha software which simplify your life on development & the working deployment proccess to upload your apps to google play / apple store with phonegap. you can even upload on your own store using alpha software .
here is video libraries for alpha click here to view it
its called alpha software , i have used it and still using it for over 10 years.
it can accept any web language such as html , html5 , js as for db it may work with almost all available DB's such as access , mysql , sql , oracle , mango db , here is a link for alpha software
https://www.alphasoftware.com/