Do you have any children? If so, then Family Income Supplement may apply.
http://www.welfare.ie/EN/Schemes/BirthChildrenAndFamilies/ChildRelatedPayments/Pages/fis.aspx
Unfortunately you won't be able to claim any Jobseekers payment while you work 6 days a week. Even if you work just one hour in a day, you are not considered to be unemployed on that day. You must be unemployed for at least 3 days a week to receive a Jobseekers payment (also note that they don't include Sundays in their calculations, so if you're working on a Sunday then you can work up to 4 days)
You are of course entitled to be provided with a statement of your terms and conditions.
To protect any future redundancy entitlement (and other contractual rights), you would be best to ask your employer to confirm that this is a temporary reduction of hours, and that your usual hours of employment will continue as before if and when business gets better. You should do this in writing, at least once every quarter. This way he cannot argue that you agreed the shorter hours and if he has to make you redundant in the future, any redundancy payment will be based on your previous full-time hours!!!!
You are technially on systematic short-time if your hours have been more than halved. If this short-time continues for a period of 4 weeks, you can apply for voluntary redundancy (provided you have the 2 years service) if you wish. With 2 years service you would have an entitlement of 5 weeks pay (at your full-time hours) as a redundancy payment.
You should talk to your employer about this. He may be prepared to offer you the same hours on fewer days, which means you could claim Jobseekers Benefit for the other days. If he's not for budging, you could perhaps use the voluntary redundancy situation as a bargaining tool and say that unless he reduces your days instead of just your hours, that you may have no alternative but to apply for voluntary redundancy.
Before doing anything, I would go in and speak to someone in your local Citizens Information Centre. If you're in a trade union, you could also speak to them (or join one if you're not!)