There is no forcible way of making sure a male will appear, but you can increase the chances of a male appearing!
Cute Charm is the answer! It makes Pokemon of the opposite gender appear in the wild 66.67% of the time regardless of gender ratios, when in the first slot of your party. If I were you, I would catch a Skitty from Route 4: it has Cute Charm, and you are more likely to find it female anyway.
These are all the Pokemon with Cute Charm:
- The Clefable Evolution Line
- The Wigglytuff Evolution Line
- The Delcatty Evolution Line
- The Cincinno Evolution Line
As for the second question, no, the pearls have no special effect when give to a Clampearl. It's just still going to be an ordinary pearl.
If you want to find out how clampearl evolves, it's right here:
Clamperl evolves by holding an item whilst trading, so you may be getting that item mixed up with pearls.