1) Yes, mikveh immersion is permitted during the nine days.

Preparation for the mikveh is not viewed as bathing for pleasure and therefore the usual preparation routine is permitted during the nine days, so long as one concentrates on preparing and does not spend extra time luxuriating in the bath. There is debate among halachic authorities about married women shaving body hair during the three weeks, so it is best to check with your rabbi about this.

2) Yes, marital relations are permitted on all of the nine days with the exception of Tisha B'Av. Some communities have a custom of refraining from relations over the nine days, but this is not widely practiced (certainly not by couples trying to conceive).

3) There is a stringent practice not to have relations on the tenth of Av, but it is waived on a mikveh night or when a husband is departing for a journey. Having relations for the purpose of conception would also override this stringency.

Although having relations at night is the preferred practice, relations are permitted during the day, as long as the room is darkened with shades or heavy curtains (which are securely attached) so that there is no direct light on you.