You have a lot of similar rules changing the font size in different areas of your CSS, and I think the source of the font issue is with how all of those rules combined were working together. Some of your rules update font-size to 34px and some to 1.2em.
I see that you've patched the problem by adding the following rule to override the others:
@media (max-width: 800px) {
h1.entry-title,
h1.entry-title a,
.entry-content h2,
.entry-content h3 {
font-size: 1.2em!important;
}
}
In that set, the 1.2em is applied to post titles once for individual post views (for "h1.entry-title") and twice for post titles on the home page (for "h1.entry-title") because they are also links. You'll see this if you compare post title size on the home page compared to single posts. That's because the 1.2em is a relative font size and is compounded if applied to the same element more than once.
If you take the "font-size: 1.2em!important;" rule out, then I think this rule was being applied for the iPad (which made it look large in contrast to the smaller iPad screen and different compared to other fonts which may have been getting set relatively (using "em" instead of "px").
.entry-title {
font-size: 34px
}
You also have other rules such as the following which would override the title font size in some cases.
.singular .entry-title {
font-size: 28px
}
Since you have so many rules in your CSS for the same thing overlapping each other, it can get a bit confusing. Using the !important rule to override things can work, but if you use it too many times then it can become a mess to work with. What you should do is make sure you understand how CSS specificity works. More specific rules get precedence. The more detailed the selector, the more specific it is (for example "h1.entry-title" is more specific than ".entry-title"). Also, if there are two rules for the same thing, the one that appears last gets precedence—so later rules are more specific.
To learn more about CSS specificity, see this tutorial:
http://www.htmldog.com/guides/cssadvanced/specificity/