I've tried fixed bid. However, whenever I do a fixed big project it takes longer than I expected and it ends up costing me. Obviously that means I'm under-estimating and/or not charging enough. Or perhaps it means the way I come up with the fixed cost is wrong.

Generally, I break the project down into a list of tasks. Estimate liberally for each task, then multiply the final number of hours times 2 then multiply by my hourly rate.

To your second point, as a small 1-2 person company, how could I afford a sales person? Are there sales people out there who would purely work on commission?