1) I inserted the table but after saving the tt_news record the table started disappearing

2) <p> tag was not inserted automatically for press of Enter

After doing some research I found the solution

1) Set the transformation mode for the RTE to “ts_css” in ext_tables.php

ex-

if (t3lib_extMgm::isLoaded(‘css_styled_content’)) {
t3lib_extMgm::addPageTSConfig(‘
# RTE mode for table “tt_news”
RTE.config.tt_news.exampleField.proc.overruleMode=ts_css’);
}

Here the table used is tt_news and the filed name is exampleField

2) For P tag to be inserted for every new line character I added the code

$rowfrntbl[$tblcol]=$pObj->local_cObj->stdWrap($rowfrntbl[$tblcol], $pObj->conf['general_stdWrap.'])

Here I am using hook  for tt_news to get the desired result.