Apache Solr and cron on Media Temple dv

Hello everyone,
I have been trying to install Apache Solr module for the last couple of days. After searching on drupal.org and google. I have successfully installed Java and SolrPhpClient, and got the Apache Solr module up and running.

Reference links:
http://www.jaysonjc.com/2008/01/13/installing-java-16-jdk60-on-mediatemp...
http://drupal.org/node/343467

Now I have several questions regarding the apache solr module:

1.
The apache solr server switch itself off or disconnect from time to time for some reason that I don't know. I got "The Apache Solr search engine is not available. Please contact your site administrator." all the time. and I have to restart it manually from ssh. But after I ran java -jar start.jar, it didn't display the prompt([root@mydomain.com]#), I am using Terminal on Mac. And apache solr server disconnect when I quit Terminal.

2.
I can not set up the script to start apache solr server automatically by following the instructions in this node:
http://drupal.org/node/545368.
I successfully created the script and added it to the service. But when I tried to start solr by using "service solr start".
I get and error message:
Error occurred during initialization of VM
Could not reserve enough space for object heap
(I also post this question on that page)

3.
I understand I need to run cron in order to index the site. But I couldn't get it running after reading these posts:
http://drupal.org/node/205118
http://drupal.org/node/271617
I set up mine like so: 15 * * * * /usr/bin/lynx -source http://www.mydoamin.com/cron.php
I get email every 15 minuntes saying: 404 file not found, The requested URL mydomain.com/cron.php was not found on this server. But obviously it's there and the permission is right.

Thank you