Type 3 - The Achiever
Type Threes work hard to achieve their goals and success. They are good at seeing what's possible and figuring out how to get the job done. They value and know how to make a good impression. Emotionally, Threes contain their feelings and offer a friendly and optimistic face to the world. They have difficulty acknowledging their deeper feelings, and they can overlook the emotional needs of others. Three's absorption in their own pursuits can lead them to overtax themselves and the people around them.
INFP
INFP's are quietly idealistic and interested in being of service to others. They are creative, have quick minds, and are able to see possibilities. They are contemplative and have a well-developed set of principles by which they live. They are loyal and compassionate, but need lots of time alone. They are modest to the point of being self-critical and are sensitive to feeling rejected. They do well when they are acknowledged for their depth of feelings and ideas.
As a Three, I'd say that the Three description is pretty good.
Overtaxing others does happen, and it's not something that most descriptions address. When the Three picks up the workahol, the people around him have to pick up the slack in every other area of life. Bravo for addressing that.
Intuitively, we'd think that an INFP / 3 combination is pretty much impossible. But taking a look at the descriptions, there's no reason why both can't fit at the same time to some degree. Both hate being rejected and want to be accepted, and they're both sensitive in that way. And, as your descriptions say, both see can see possibilities and act upon them.
The only problem in combining these two types is that we're stating that the participant can't find his feelings and that, at the same time, he wants his feelings to be acknowledged.