Fleetslots and Probe questions

I am currently limited to 7 or eight slots. How can this number be increased. Also, is there an actual advantage to sending in more than one esp probe? For example, I send one and it is lost. If I had sent 5, would I be more likely not to get exploded? Is it all espionage level?

So for starters, fleet slots come from comp tech... higher comp tech more slots... as for the esp issue, more probes can reveal more information... probes are destroyed by counter espionage see below

http://ogame.wikia.com/wiki/Counterespionage