Is there any way to force JSF2 not to change ids?
You can set prependId="false" This way in generated HTML it will be from in place of  j_idt8:from.
prependId : Flag indicating whether or not this form should prepend 
 its id to its descendent's id during the clientId generation 
 process. If this flag is not set, the default value is true.
How can I get this element in e.g. jQuery?
You can use ancestorComponent:from in jQuery to get this element.
Actually j_idt8 in j_idt8:from is auto generated id of ancestor component of your <h:inputText/>
for example 
<h:form id="form">
<h:inputText id="from" value="#{fromToMBean.fromName}"/>
</h:form>
Now generated id of input text would be form:from
If you don't provide id to a component than your browser generates that dynamically. So don't forget to provide ids to components.