splendide
Firstly, if your child seems a healthy weight now and mealtimes are happy affairs you are probably doing fine 
and you are obviously well informed on processed meat so you are I'm sure well ahead of most people!
A couple of practical suggestions:
Start with very small portions. He's more likely to eat some of everything if he doesn't have the chance to fill up with the bits he likes best or that he is most familiar with at the start of the meal. We work on the very simple principle that if a child wasn't hungry enough to eat what was on their plate then they definitely aren't hungry enough to need anything else. When the plate is clear he can always have more.
Remind yourself that despite the difficulty you had at the start, a child is far, far more likely to have health problems from being over fed or from being fed a limited diet of processed food than they are from occasionally turning up their nose at what's on offer at lunch and going without until dinner time. So for the sake of mealtimes being street free and your child eating the right things I propose no battles - if he doesn't want it he doesn't have it - but no cracking and giving him something else when he whinges he's "starving" an hour later.
If you are mostly feeding a wide variety of unprocessed foods, heavy on vegetables and including some oily fish and your child is a healthy weight then you are unlikely to be going wrong.
In simplest terms for portion size, I think about what is a reasonable portion for an adult of a particular food, and the size of an adult vs the size of the child and scale up or down accordingly. If you are 3 times bigger would you be OK with eating 3 times the portion of blueberries that your child wants to have or would it be totally OTT? If so say no and offer a carrot to gnaw on instead. My general principle is "you aren't hungry enough for a vegetable then you aren't really hungry".
Where fruit is concerned it does get complicated. I'm very sceptical of things like the food pyramid and '5 a day'...billions is spent by multinationals lobbying ational governments and the EU on these types of campaigns. I think all of the academic studies that persuaded the government to count smoothies and juice in '5 a day' were funded by cocoa-cola and other multinational selling smoothies and juice. 
Like him or loathe him, at least Jamie Oliver gives a voice to the other side that doesn't want to sell and serve highly profitable processed foods
Of course fruit is great because it is heavy in micro nutrients. However, unlike vegetables it is also high in sugar (kids are biologically programmed to seek out sugar to ensure they love milk as infants) so some kids, if allowed, will definitely eat far more fruit than is good for them. Some fruit is more sugary than others though and blueberries are on the better end of the scale but variety is also important as different fruits have different vitamins/minerals. I limit my kids generally to 2 portions of fruit a day with a portion of about half an 'adult' fruit, so half a banana (having 2 kids makes that easy!). I'd give them a whole 'fun sized' apple or tangerine. I also only really give them fruit at mealtimes. Eating fruit with other foods and also the fibre in whole fruit itself slows down how quickly your body can process the sugar (why drinking a juiced orange is different from eating that same orange whole) and get it into your blood, but sugar is still sugar and despite all the nonsense about 'natural' sugars, what's in fruit is basically the same as the granulated stuff which started in a vegetable (beet or cane) but has been separated out. We also now know that consuming fructose alone doesn't trigger the natural 'you are full' messages that the body sends the brain which is why some kids can get through vast quantities of calories worth of fresh or dried fruit and still not feel full. This is why it's not only what you eat, but how and when you eat it that matters. Eating a potato followed later by a chop followed later by a portion of cabbage is not the same for your body as eating them together in a single meal. As well as the speed in which the glucose is converted into into your blood, the second reason is that many micro nutrients work in combination and can only be used when the other necessary vitamins and minerals are also present.
We don't do snacking here for loads of reasons including that micronutrient benefit. It is also shockingly bad for teeth. The natural process is that after eating the mouth neutralises acids from the food that attack enamel and 'rebuild' the enamel. If children are eating (or drinking anything other than water - milk is high in sugars too so keep it for mealtimes and think of it as a food) between meals then the teeth are constantly under attack with no repair time. That is also why teeth should be brushed before breakfast and not immediately after when teeth are weakest (you probably know that but I had been doing it wrong for years!). Secondly, snacking doesn't give the body time to stabilise the blood sugar levels so the body becomes reliant on a steady stream of sugar spikes and when they stop you get the blood sugar crash effect. Most importantly, snacking means that your kids are less likely to be properly hungry at mealtimes and if they are not properly hungry they are more likely to be picky and refuse what's on offer.
And here ends the lecture