3 questions

@Cattext:
1. You can change the font size in the following css as per your need and then add it in “Appearance => Theme Options => Custom CSS” box:

.header-sidebar .widget ul.menu a {
    font-size: 16px;
}
.header-sidebar .widget ul.menu ul a {
    font-size: 14px;
}

2. You can add the following css in “Appearance => Theme Options => Custom CSS” box, to reduce the space above search box in header right section.

#header-right .widget.widget_search {
    margin-top: 0;
}

3. So, after you add title for alt tag and want to remove the title from the slider then you can add the following css in “Appearance => Theme Options => Custom CSS” box
#main-slider .entry-container { display: none; }

@Cattext: For #2, you can adjust the padding in the following css and then add it in “Appearance => Theme Options => Custom CSS” box:

#hgroup-wrap {
    padding-bottom: 50px;
}
#main {
    padding-top: 50px;
}