iRule redirect and specify what Pool to go to

1)

OK. Just be mindful that a postback on the page would expose the filename of the page, which users may bookmark.

2/3)

If you don't have a default pool you will not have any health information available for that VIP. If you do have a default pool the entire VIP will be taken down if the default pool goes down.

Are you using SSL or planning to use it in the future? If so you'll want to set up dedicated VIPs.

As far as your iRule error go, they're caused by an invalid "elseif" syntax. Firstly, you can't have comments between the closing curly brace and the "elseif" command. Secondly, the "elseif" command needs to immediately follow the curly brace:

} elseif {