No, you do not have to have 100% bonding to marry (in fact one of my friends had no bonding at all if I remember correctly). You only need 100% bonding if you have a Mametchi, Memetchi, Kuchipatchi or Furawatchi/Violetchi and want to get a Mame, Meme, Kuchi/Kuchipa or Furawa/Violet family, or if you want to have a chance of getting the space characters on your next generation.
Easiest way I found out how to (and I take no credit at all for this) is to adjust the time.
It took me about.. 1hour to get 100% Bonds so very very helpfull.
Go to the time>adjust the time/date(press C & A). And enter in either of the following times:
9:57am
11:57am
1:57pm
3:57pm
5:57pm
When the time changes to either 10am, 12pm, 2pm, 4pm or 6pm you will need to train your tamagotchi's. Doing this 2-3 times gets your bonds up by at least 10-20%.