It's a difficult question to answer, as the nature of what a "Technical Manager" is will vary between businesses, and I can think of plenty of food businesses (including some fairly large ones) where no employees have this as their job title.
The key element is more about responsibility/knowledge/authority, IMO - i.e. who is responsible for the relevant food safety systems, practices etc, do they have the requisite knowledge to perform the role, and do they have the authority to make decisions and changes when required.
I terms of the "reassuring to have his knowledge" element, this is a natural part of being a human that does not have a politician-sized ego, IMO 
I've been a technical manager for quite a lot of years now, but recognising that there are plenty of things I don't know is key to being good at my job. Assuming you know everything, or that you'll always make the right decision every time, is a recipe for problems, based on a good number of examples I can think of but can't explain for contractual reasons. I'd argue that one of the important skills as a more senior technical person is recognising the deficiencies in one's own knowledge, and knowing where to look to do something about this.
Having the confidence to make decisions without the backup of a trusted mentor is certainly one of the more nerve-racking parts of progressing in your career, but it's something that can really only come with doing it. Just know that you won't always make the right call - no-one gets it right every time 
As a QC you should also always be aware that it is similarly ok to push a decision up the management chain, if you genuinely feel that you don't have full confidence/authority/knowledge to make it.
So, will they have to employ a tech manager? or is the director and then myself as QC sufficient?
The answer to this question is a definitive "maybe".
If they aren't going to employ a technical manager (or someone in that type of role - whether they call them a QA Manager, QC Manage etc) then you'll want to make sure that responsibilities are clearly defined, that you're given the authority to do what's expected of you (for example, a robust debate with a production manager is sometimes easier if you're on equal footing with them in the management structure), and that you have the support to progress towards that role, if that's what you want and are expected to do.
By implication it seems that unless the Tech Director is going to become far more hands-on, you will necessarily be taking on more of what the tech manager was doing. Are they going to help with your professional development towards this? Are they going to pay you more for dealing with the increased responsibility and work load?