Suggestions on how to improve this .htaccess file for page load speed
Honestly, this looks OK, though you could clean it up a little bit. 

You have two ways to make this code better: 


group related mime types.
use human-readable syntax


Regarding point #2, here's part of the config I created after watching Illya Grigorik's presentation "Breaking the 1000ms Time to Glass Mobile Barrier":

&lt;IfModule mod_deflate.c&gt;
# these are known to be safe with MSIE 6
AddOutputFilterByType DEFLATE text/html text/plain text/xml

# everything else may cause problems with MSIE 6
AddOutputFilterByType DEFLATE text/css
AddOutputFilterByType DEFLATE application/x-javascript application/javascript application/ecmascript
AddOutputFilterByType DEFLATE application/rss+xml

ExpiresActive On
ExpiresDefault "access plus 15 minutes"

ExpiresByType text/html "access"
ExpiresByType application/json "access"

ExpiresByType text/css "access plus 1 week"
ExpiresByType image/gif "access plus 1 week"
ExpiresByType image/png "access plus 1 week"
ExpiresByType image/jpeg "access plus 1 week"
ExpiresByType application/javascript "access plus 1 week"
&lt;/IfModule&gt;


You might also look into Google's mod_pagespeed for Apache.