The font size settings can be changed in backend from Extensions >> Template Manager >> JA_Sanidine >>
Attaching a screenshot. Hope it helps.
As per the css file of the template, the fonts used are :
For the body
[PHP]body {
background: #FFFFFF;
color: #000000;
font-family: “Lucida Grande”, Arial, Helvetica, sans-serif;
line-height: 1.5;
}
…….
body.fs1 {font-size: 10px;}
body.fs2 {font-size: 11px;}
body.fs3 {font-size: 12px;}
body.fs4 {font-size: 13px;}
body.fs5 {font-size: 14px;}
body.fs6 {font-size: 15px;}[/PHP]
For the headings
[PHP]/* Heading */
h1 {font-size: 200%;}
h2 {font-size: 175%;}
h3 {font-size: 150%;}
h4 {font-size: 125%;}[/PHP]
Sometimes the font problem / font size problem are also because if one simply cuts and paste from word documents or any other formatted source. It is best practice to paste the content first in Notepad (as it strips the formatting) and then paste the content in the joomla editor.