Wheeler, if you hire an attorney on your own, they have an incentive to stall the process since they are only paid out of backpay, whereas your LTD company can pay the representative directly, thus eliminating the incentive to stall. So, if you are going to get the service free via LTD, I'd recommend you accept the help. Otherwise, I'd recommend you start the process on your own. (Most attorneys won't even speak to you this early in the process, anyway.)

At 60, and with documentation of severe dementia, it is unlikely he'll have a lengthy or difficult time receiving a Fully Favorable decision. He may not see an increase in monetary benefits due to offset, but receiving Medicare is significant. (You should start researching supplement plans as well.)