increase product description length on product page ?

I have 2 Questions

1> how to increase product description length on product page?
i want to have a longer descrpition of product on product page may be 1500 words, once i enter longer description,and save the page. the description gets shortened, half of the content get deleted automatically.. and it is not visible on front end. does any one know how to increase length of product description on product page.

2> how to increase description length on html module ?
i want to have a longer descrpition in html module as my site requires to do so, when i i enter longer description,and save the module then i get following error

Notice: unserialize(): Error at offset 137 of 65535 bytes in /home/lapmumbai/public_html/index.php on line 56
Warning: session_start(): Cannot send session cookie - headers already sent by (output started at /home/lapmumbai/public_html/index.php:56) in /home/lapmumbai/public_html/system/library/session.php on line 12Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at /home/lapmumbai/public_html/index.php:56) in /home/lapmumbai/public_html/system/library/session.php on line 12Warning: Cannot modify header information - headers already sent by (output started at /home/lapmumbai/public_html/index.php:56) in /home/lapmumbai/public_html/index.php on line 175Warning: Cannot modify header information - headers already sent by (output started at /home/lapmumbai/public_html/index.php:56) in /home/lapmumbai/public_html/system/library/currency.php on line 45

I cannot login into admin... below is the error on the backend (admin page when i log in).

so i had to delete the entire site and restore the backup,

pls help me,
regards
Pravin thakur.
http://loanagainstpropertymumbai.com/