I have not tried transferring weight maps (does it work?) but I regularly move items in OBJ format between DAZ and Blender. If I want anything in parts e.g. doors, windows I export/import them seperately then position, parent and set the axes in DAZ.

Re the size issue I suggest you get a scale sample (I use a standing or sitting V4), import to Blender then scale other things to match that - then when you export the OBJ it will always be the right size in DAZ.  When you export from DAZ use the "Blender" preset and in Blender export, set it up until things match up both ways, which may take a little trial and error.  I always have to put the cursor on the centre (shift-C) then go to side view (numpad 3) in ortho (numpad5), select the imported object and rotate 90 to get it the right way up, then change whatever I want, then reverse the action (rotate X -90) before export to get things vertical in DAZ but maybe you can find a setting in the export that will fix that.