First things first, Which Matmid country are you enrolled in USA or Israel. If USA you should change your membership to Israel so that you can participate in all their offers out of the country.

Also have you read all the FQTV information on their website, it's very informative and should answer most of you initial questions.

After reading through this information you'll probably find that your best option (on the assumption that 75% of your travel is reimbursed) would be to take 'Y' fares and use your points to u/g to 'Z' or just purchase 'Z' direct.

The burn rate on the U/G isn't as good from TLV-NYC as you’re only earning 200-350 points each way while burning 700 each-way on an U/G, where as TLV-LHR the earning rate is 150 points each way while the burning rate is 200 on the U/G each way.

If you’re travelling every 5 weeks, you'll hit platinum within around 14 segments so 7 flights (discounted Business) or 25 segments or 12.5 flights (economy); this will give you a more economical way of using u/g with reduced points. Be aware that there are quite a few PLAT commuters out there.

Your Amex / Leumi will earn you matmid points.

Overall these are the main options open to you on ELAL though you should also look into Continental's BusninessFirst product or BA NewClubWorld Product thats if you don't mind breaking the flight up with a 2 hour layover in LHR on the BA flight (the C/F service LHR-NYC-LHR is worth it! and post August so will the LHR-TLV-LHR).

Hope this helps