Re the spike, it could just be bloating...lots of fruit and veg can do that at various times. I have heard that mixing fruit in with veg (salads), makes this reaction more common, but that is just 'talk', I've not found any science to it (yet). However, if you react to certain types of natural sugars (fructose, mannitol, polyols, sorbitol etc), then this could be a cause of bloating - in your list, that would be sultanas, prunes, LOADS of grapes (under 20 and you should be ok), apple, more than 1/8th of an avocado. Many people are absolutely fine; this is only for those that malabsorb these types of sugars. And some people who are fine, may find a small reaction at times...could be that this was what did it for you.
Re fruit and veg and weightloss, well this is altogether a different topic. In general, if it's FRESH, I'd say go for it. When it's dried, you are concentrating the sugars and the 'fill-up' factor of the water is less, so you can eat rather more calories than intended. Just watch portion size on the dried fruit, (and of the grapes, as these are also high in calories - the highest of all fruit, and the avocado which is high in good fats, but it is still fat). Veg, just go for it!
If you are wanting to vary the salad cream dressing with a less high calorie option on some days, try chopped chives, lemon juice and salt. I also use cottage cheese, natural yogurt, a bit of lemon juice and salt with a salad of cucumber, tomato and spring onion (really yummy!).