The answer to your 2 questions depends upon the rating or percentage of disability that the VA has given your boyfriend.
If he is rated as 100 percent disabled AND Permanent and Total, then he can't work, but his pension will never be taken away.
If he is rated as under 100 percent then it's possible for him to work and yes there is a Vocational Rehabilitation office in the VA Manila. He can apply for services with them.
Anyone that is rated as anything less than Permanent and Total can be called in for a re-examination by the VA and it is possible for them to reduce the rating and pension if they think the person's disability has improved.