A: In food businesses such as yours, marketing can be a very good stepping stone to the top (if that is where you want to get to). However in my experience, marketing often does not deliver in three key facets that are essential experiences of general management: finance, man-management and selling.
It is a good thing that you want to take the risks involved in building your experience outside your first discipline and I would strongly encourage you to continue taking responsibility for a part of the sales team could give you momentum and identify you for fast tracking.
You are fortunate that being in marketing you can find good reason to speak to mangers in finance, sales and operations, and sound out what opportunities there are in joining their teams, perhaps for a secondment or project. There may also be opportunities in approaching a senior manager to mentor you through this transition, if only to bounce ideas around before decisions are made.
The 'watch out' here is whilst building your new skills, do keep your marketing contacts alive as you never know when you might want to revert. Make sure you also share your thoughts with your manager as it is essential you leave with his blessing.
A: Tunnel vision is both a compliment and a criticism; the skill is in combining the two. I recall a senior Shell manager offering the view that helicopter quality was the most important skill of leadership. By this she meant being comfortable with the details, the muck and bullets of project management, and then being able to lift off and see how the project fits into the business' goals.
The key question here is who is criticising you one of the ways for detractors to slow innovation is to make the assertion that a particular change is out of kilter with his part of the business, and therefore cannot be implemented. I suggest that you reference back to senior management for a brief review of project status.
In my opinion, project management is about first-class communication, and then boldness. Make sure you are getting an 'A' in both. It is only in dotting i's and crossing t's that you can deliver success.