If it were me, I would;
1. Get his X-rays to at least two of the top resurfacing surgeons (you can get the info on this site). Ask them to determine the cause, and what course they suggest.
At some point you may also want to get an MRI in order to determine if there is any soft tissue damage around the joint from the high ion levels, but I would leave that up to the surgeon you eventually decide to use.
2. The most common cause is cup placement, which they will be able to tell from the X-rays. If that is the cause, he will need to decide whether it will be possible to replace the cup, and retain the resurfacing. This decision may be influenced by what brand it is, and how healthy the bone looks around the femoral neck. Only a few of the top surgeons will use this approach, as most will want to do a total revision.
3. Since he already has problems, I would go to one of the best surgeons in the world that you can afford. If he has an ASR, you should explore avenues for having them at least cover your expenses.
If the ion count is really that high, the consensus is that he should not ignore it, and needs to pursue having something revised before there is too much tissue and bone damage.
Good luck, and good for you for stepping up to help him through this.