Unicast Flooding due to Asymmetric Routing

Rene,
Great lesson, however I have a questions if you please clarify.

How do I change the ARP table timeout so it matches the aging time of the MAC address table.?
How can we make one vlan as gateway if we have multiple vlans on the distribution switch connects to different closets on the floors? For example we have
vlan 2 - serves second floor and it is on our distribution
inter vlan2
ip address 192.168.2.1/24

vlan3- serves 3rd floor
inter vlan 3
ip address 192.168.3.1/24

In the closet 2 floor access layer switch has an ip address of 192.168.2.5 with default gateway of 192.168.2.1.
Same topology is applied for other floors.

Thanks
Hamood