Added .lowercase-alpha-list now my list is adding an extra period

So, the theme is adding it as a :before but it’s not a character or ‘content’, instead it’s using a height and width value and then a background colour:

.text-entry li:before{
    background-color: transparent;
}

That ought to do the trick.

You could even go with the nuclear option:

.text-entry li:before{
     display: none;
}

Or… …a more comprehensive version of the first rule:

.text-entry li:before{
    background-color: transparent;
    width: 0;
    height: 0;
}

Just make sure this CSS loads after the theme’s CSS.

What I would recommend however, because the theme obviously has that rule in there for a reason, is that you try and use your class that is on the <ol> element to make the rule more specific, so that you only apply this effect to this particular list.

So maybe like:

.text-entry .lowercase-alpha-list li:before{
    width: 0;
    height: 0;
    background-color: transparent;
}