1. A profit exceeding 10-15% is not necessarily unreasonable. The Weighted Guidelines method is required in some instances for the Government to arrive at a prenegotiation objective, but it does not limit what a prospective contractor can propose. It has as much relevance to the negotiation as the method the prospective contractor used to develop their prenegotiation profit objective. As far as what the contracting officer said about the board, that may be true. But that doesn't mean you have to lower your profit. The Government will need to decide if what they need is worth agreeing to what they consider an unreasonable profit. Is the Government ok with your bottom line price?
2. See FAR 31.205-7 regarding the inclusion of contingencies in cost estimates.