Hi there,
1. in Customizer > Colors > Buttons you can change the background and text colors.
1.1 The border is added using this CSS in Customizer > Additional CSS:
button, html input[type=button], input[type=reset], input[type=submit], a.button, a.button:visited {
border-width: 1px;
border-style: solid;
border-color: inherit;
border-radius:3px
}
You can delete this if you want to remove the border.
2. Try adding this CSS:
.read-more-button-container {
margin-top: auto;
}