10k NIS is fairly normal for someone that age. In terms of the age difference, it is a suggested range. I’m sure if you suggested a 46-year-old he wouldn’t say no. The lower limit of 30 is a way of showing potential shadchanim that age difference doesn’t matter. A shadchan who sees 48 might not think to suggest a 37-year-old but by saying 30-45, it gives them the hava amina. It is all a mind game to get you to suggest shiduchim.
Shopping, the reward is for helping him find a wife. It is not different then paying a Shadchan for his/her help. The only difference is that he is asking the public for assistance in finding his ??? ???. By offering such a big reward he is demonstrating that he is serious (and desperate). I don’t see anything wrong with it.