How can I remove or lower the number of charactors in the /places page?

This CSS will hide that but should be targeted to the page you are working on.

div.geodir-entry-content {
    display: none;
}

GDV1 doesn’t have display options for the post content field

Well, let me clarify.
CSS is good for off/on.
There are settings.
If it is a shortcode then the settings for char length are in the shortcode.
If it is a page, then the options are in
GD – Design – Listings – Description word limit

These settings apply only to the listing page:
GD – Design – Listings – Description word limit

Limiting input count is done in the price package.