The command did not work for me:

[root@tekgoblin ~]# mysqldumpslow
Can't determine basedir from 'my_print_defaults mysqld' output: --datadir=/var/lib/mysql
--socket=/var/lib/mysql/mysql.sock
--user=mysql
--old_passwords=1
--long_query_time=1
--log-slow-queries=/var/log/mysql/mysql-slow.log
--max_connections=300
--key_buffer=32M
--myisam_sort_buffer_size=32M
--join_buffer_size=1M
--read_buffer_size=1M
--sort_buffer_size=2M
--table_cache=4000
--thread_cache_size=286
--interactive_timeout=25
--wait_timeout=7000
--connect_timeout=10
--max_allowed_packet=16M
--max_connect_errors=10
--query_cache_limit=2M
--query_cache_size=12M
--query_cache_type=1
--tmp_table_size=16M
--skip-innodb
[root@tekgoblin ~]#

I lowered requests per child to 200 and now i am getting around 1400 hits in less than an hour to the site and its handling them fine:

http://imgur.com/yKrrT.png

However and I typed this, this happened:

http://imgur.com/qIceS.png

Your MySQL config seems fine memory-wise, and it actually isn't using that much memory according to the top output. (But why is mysql_sort_buffer_size so big? You probably don't need more than 2M unless you're doing something monstrous.)

The culprit, as usual, is Apache. It's using 700-800MB of RAM according to your last screenshot. With 24 heavyweight children, this is only to be expected. There really are very few options, all of which has already been discussed. Cache the hell out of everything, drop unnecessary WordPress plugins, and reduce MaxClients/ServerLimit. (Reducing the max requests per child only helps if the PHP engine itself has a memory leak, which is unlikely nowadays.)

Most importantly, set up a Linode 768 or 1024 and run some stress tests. It's been 6 weeks since you've been posting here, so there's no reason not to try a Linode already. If you're not satisfied with the results, you know Linode has a 7-day money back guarantee.