homebertha, what a shame your HV came out with such unsupportive stuff :( :(
HVs are under pressure to pay attention to their local obesity stats, but this has not come with any real training to improve their support for bf - and support for bf you probably know is actually part of national anti-obesity programmes. It sounds to me that she is confusing ff with bf - 3-6 ff a night would not be a good thing, but breastfeeding is different. It is physiologically normal for a baby to breastfeed several times in the night and at this age, restricting this could be very distressing. In any case, if there is a real issue with your baby's growth, a sensible, informed person would not suggest sudden changes or making your baby unhappy in this way.
Breastfed babies self-regulate in a way formula fed babies find harder to do. A baby whose height and weight are like your baby's is almost certainly just fine and if you continue doing what you are doing, he will 'even out' in time, when he becomes active (at 7.5 mths babies are not able to do the crawling and cruising and walking that burn energy).
The key to healthy eating is to ensure his solid foods are nutritious and not 'junk' and you probably already do. He can feed himself (baby-led weaning style) and gradually increase his repertoire of tastes and textures.
Review things when your baby is 12-15 months and the picture will probably be very different :)
It might be useful for you to seek a second opinion on all this, to boost your confidence, and to check there really is nothing to be concerned about - no one here can actually see your baby and we can only go on what you have written here :)