4.) Maybe try this?

.comment-poster span {
margin-top: 0; }

span.ljuser {
margin-top: 2em; }

5.)
.metadata-item-xpost {
background-image: url("image url");
background-repeat: no-repeat;
margin-left: 0.6em;
padding-left: 26px;
margin-top: 1em;
margin-bottom: 1em;
height: 16px; }

5.a) Couldn't figure out how to change the space between the currents and the tags, but here is the code to change the space between the currents:
.metadata-item {
margin-top: 0 !important;}

I think that's about as much help as I can give! Good luck!