Ajay Krishna, BDS, MDS

If the infection is small you can try having a reroot canal treatment but if the infection is large in size and there is pus discharge it is always better to extract the tooth and go for replacement of tooth with a Dental Implant.

Because you have teeth grinding habit. There is a high possibility of implant failure due to abnormal forces ,please visit prosthodontist and try to adjust the occlusion, your implant tooth should not come in contact with the opposing tooth during rest position and if possible start using a soft splint ( Night Guard)

you can get the composite bonding to close those gaps between the front two teeth (Dark triangles).I think You will get a reasonably good result with the bonding.

Please go see a dentist and get an xray of tooth , if the damage is minimal dentist would prescribe antibiotics and stabalize the mobile tooth with spllinting and put under observation for couple of weeks ,If the damage is severe he would extract the teeth and place an immediate implant with a temporary tooth matching the colour of the adjacent tooth. Do not worry with the recent advancements in porcelain materials you can have an artificial permanent tooth exactly matching your natural tooth colour.

your smile looks good.Its just that the tooth show up is more when you smile. I would advice try getting filler injections to correct the gummy smile . It will show less tooth structure when you smile ,its safe and reversable process and if you dont like your smile  than you can opt for crowns at latter stage.