no the series hasn't ended yet but they do have strong feelings for each other :)
Faithshipping.
no
Japanese duel disks are pretty small, Yusei's included. That black guy in Yu-Gi-Oh Millenium World, whatever his name was, had a massive disk though.
Yusei, joined by Jack and Crow, Duels Goodwin in episodes 62, 63, and 64.
During the Yu-Gi-Oh! 5D's arc, Jaden Yuki is older than Yusei as the series is set many years after Yu-Gi-Oh! GX. However, during both series, Jaden and Yusei are 18 years old, meaning that they are the same age during their respective anime series.
Faithshipping.
No
This is not shown in the anime. However, it is hinted that Yusei Fudo and Akiza Izinski (Aki Izayoi in the Japanese anime) harbor feelings for each other. This is not yet confirmed.
18
no
no
Of Course She Does. She is strongly focused towards him but, yusei definitly cares her as a friend ,the hint is in: yu-gi-oh 5d's episode 117 when he tried to save her from being sucked inside a wormhole. yusei in love with aki, there is a hint in the ending 5.
not sure
episode 56
yu-gi-oh! 5ds
By completing yusei's story.
if your talking about the one in the first season then its yusei