"omain.com/news it doesn't redirect domain.com/news/"
"Also when the url ends with .htm redirection doesn't works..."
That means your source doesn't match the requested url. Create a redirection that matches that in addition to the one you have that's working (or modify your source to a regex that matches both).
EG: Using a regular expression you can only .html posts that by:
Where the brakets mark out the parts the regular expression applies;
/ = /
(/d*) = any number of digits, when the next character is not a digit it must be
/ = /
(.*?) = Any number of characters or digits [the .* is any quantity of, ? is any character but won't match spaces if I remember correctly)
finally ending in .html
For me this matches
/2012/11/my-post-title.html and turns it into /2012/11/myposttitle/
I made some notes for myself on my blog