[Plugin: Pronamic Google Maps] – strange behaviour

Hello,
I recently realised a museum site with a museum search page. The museums for a certain combined search (by country, city etc.) are listed in rows and also displayed as markers on a Map, I am using Pronamic Google Maps plugin. This is the page address:

http://www.inexhibit.com/mymuseum

Now I have two issues:

1) The page is “messed up” until the markers building up is fully completed, in the meanwhile a text list of museum is displayed instead of the correct page layout, thumbnails and titles.

2) I have only 150 museums listed (my plans is to have about one-thousend of those in a short time) but the page seems me already very slow, particularly when I do a search reset.

Is there something wrong in my plugin implementation or it is just a limit of Pronamic GM?

Any help appreciated!
Riccardo