2. Yes, I would recommend you to create a static block and set it in Footer Column 1 widget area.
Read more – https://xstore.helpscoutdocs.com/article/48-widgets-custom-widget-areas https://xstore.helpscoutdocs.com/article/47-static-blocks
3. Please add this css code in Theme Options > Styling > Custom css:
footer .mc4wp-form .et-mailchimp input[type="email"] {
color: #999;
margin-bottom: 15px;
width: 100%;
background-color: #fff;
}
.mc4wp-form .et-mailchimp input::-webkit-input-placeholder {color:#999;}
.mc4wp-form .et-mailchimp input:-moz-placeholder {color:#999;}
.mc4wp-form .et-mailchimp input:-ms-input-placeholder {color:#999;}
Regards