Here is my views on these ones:
1. Weetbix - I tried the adult stuff on and off from about 9 months with DD but it reacted which was so annoying. It was just too heavy for her tummy at the time, she had some sensitivies though. The Kids Weetbix is awesome, DD has been on that for a month (or so). It says for 1-5 year olds so its really your call whether you try it before. If your keen, just try a small bit and monitor your bub for a day - see how it effects their bowl movements etc. Most babies seem to do just fine with it. I think it is an excellent breakfast, quite nicely balanced, convienient and easily 'jazzed up' with some fruit, yoghurt or even some sugar.
2. The variety thing is an interesting question. I think as long as you balance their diet daily, as close/practical as possible, then variety isn't such a big issue. If you happen to have a stack of one veg at home (for example, carrots on special) then it doesn't matter if you serve that up a few nights in a row. I some times mix veg together, some times serve separately, some-times hide it in meat (and so on) - do what ever works for your bub, which usually changes daily - lol. I think the key is to always serve one thing you know your bub will enjoy. That makes it easier to 'hide' other things with it (new foods etc) as well as being confident they will more than likely eat some-thing.
3. Tomatos are a dodgy one. They are on of the highest possible reacting veg/fruit around as they are full of chemicals. I'd go gradually with this one as can really irritate a bub. Maybe give a small mouthful of your own bolognaise, what ever you usually make for your self. Although, might want to add a little less herbs, onion etc. If bubs goes ok, then next time you have it - try a couple more spoons. personally, I think a tin of diced tomatos mixed in with some mince, spaghetti and some grated cheese is yummo. It can be fun finger food for bubs or you can mash it all up and spoon it in.
4. I have only taken fruit jel and custard out and that has been just fine if sat in my bag for an hour or so. I'm really not sure about meat though, probably would avoid it personally (serving without heating that is).
5. You are right, some of the bought baby food stinks - especially that pumpkin and sweet corn, makes me want to gag. I always though it was just the combination of food. Their fruits and gel's are really nice smelling (and tasting - lol).
6. I took ages to give DD biscuits as wasn't happy with the ingredients. I have made my own which are a much better option. Now I get the Little Kids range which have some great cheese crackers that are a much healthier option. I tried arrowroot a few times then stopped. DD was gagging on them constantly - they break of in chunks and get very crumby so DD would caugh and a spray of like dust would come out. If asked, I don't recommend them. There are healthier and in my opinion, safer options out there.
DD is 3yr 8 months - DS is 6 months