.htaccess help needed - Important

I am running couple of sub-domains via our main domain: http://www.mydomain.in
Sub-domains in use:
http://forums.mydomain.in
http://gallery.mydomain.in

I am having some serious issues with this domain as follows:

1. Serps + Guests are able to get to my sub-domains from following URLs as well:
www.mydomain.in/forums/somepage
forums.mydomain.in/somepage
000.000.000.000/forums/somepage
This is creating lot of dupe content, i want to fix this problem, with a 301/permanent re-direct (without loosing any rankings or getting penalties)

2. I am running a forum software script, any user typing a wrong URL or trying to access any improper location should to be re-directed to the root. I want to achieve following if a user tries to access:
forums.mydomain.in/showthread.php?t=1233 which does not exists (reason got deleted)
should be re-directed properly to forums.mydomain.in

3.
There are many pages indexed in Google and Yahoo via our Site IP Address as well for example:
000.000.000.000/forums/somepage
I want to re-direct such pages to forums.mydomain.in/somepage

4. While trying to re-direct users from 404 URLs on forum, entire .CSS and image paths appear to be invalid, is there a possible solution for re-directing users from 404 pages to root properly?


This are my .htaccess files:
This are the .htaccess files on my domain currently as follows:
########################################
#http://www.mydomain.in/.htaccess#
########################################
ErrorDocument 400 /
ErrorDocument 401 /
ErrorDocument 403 /
ErrorDocument 404 /
#
Options +Indexes +FollowSymlinks
RewriteEngine on
RewriteBase /
#
# Prevent duplicate content on gallery and forums subdomain
RewriteCond %{HTTP_HOST} ^(gallery|forums)\.mydomain.in
RewriteRule ^(gallery|forums)(.*)$ http://%{HTTP_HOST}$1 [R=301,L]
#
#Re-Direct users coming to forums and gallery via IP Address in SERPs index to proper location
RewriteCond %{HTTP_HOST} ^000\.000\.000\.000
RewriteRule ^(gallery|forums)/(.*)$ http://$1.mydomain.in/$2 [R=301,L]
#
#Re-Direct users coming to Site via IP Adress to proper location
RewriteCond %{HTTP_HOST} ^(000\.000\.000\.000|mydomain\.in)
RewriteRule (.*) http://www.mydomain.in/$1 [R=301,L]
########################################

########################################
#http://forums.mydomain.in/.htaccess#
########################################
ErrorDocument 400 /
ErrorDocument 401 /
ErrorDocument 403 /
ErrorDocument 404 /
#
Options +Indexes +FollowSymlinks
RewriteEngine on
RewriteBase /
#
#Re-Direct users coming to /forums/ to proper subdomain
redirect 301 /forums/ http://forums.mydomain.in/
########################################

########################################
#http://gallery.mydomain.in/.htaccess#
########################################
ErrorDocument 400 /
ErrorDocument 401 /
ErrorDocument 403 /
ErrorDocument 404 /
#
Options +Indexes +FollowSymlinks
RewriteEngine on
RewriteBase /
#
#Re-Direct users coming to /gallery/ to proper subdomain
redirect 301 /gallery/ http://gallery.mydomain.in/
########################################

1. Please check the above codes those are working perfectly fine on my domain currently, if you can further provide some more optimizations if needed please let me know.

2. Will i face any problems in future/present using those .htaccess codes? I dont wish to loose my listings/rankings.

3. I dont want to loose the indexed contents via IP Address (lakhs of pages indexed via IP) and also via improper domain handling.
i.e., www.mydomain.com/forums/ (lakhs of pages indexed via improper domain URL)

 

is there anyone on internet who can help me fix my problems ?