Hi :) New to MFP with a few questions

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Hello everyone! This is my third day of MFP-ing, and I'm doing ok so far, I think! Resisting the temptation to jump on the scales until at least the weekend though, I know any loss I see this soon won't be 'real'.

I have filled in my profile etc, so there is a bit about me there, I won't repeat myself here, except to say I am female, 31 years old, 5'4", and aiming to lose about 28-30lb. I lost 26lb last year with Slimming World, but have put on about 3/4 of that again in the last 7 months or so. I'm currently 11st 9lb. Since I was about 24, I have yo-yoed up and down in weight, with my lowest being 9st 7lb and highest being 12st.

I have been vegetarian for 18 years, though I do eat 'meat substitutes', mostly quorn. This is for two reasons: I gave up meat because I didn't like the taste or texture, and I find quorn fine for both. Also it makes cooking easier, since my husband is omnivorous, so using quorn means we don't have to make two separate meals if we are having lasagne etc. I have IBS, so tend to limit my insoluble fibre intake, but am fine with most other things. Total chocolate addict though :(

Slimming World is the only 'proper diet' I have been on, so I am not used to calorie-counting. One of the things I want to ask is how to divide up my calories during the day? My calorie allowance is 1440 according to MFP, and I usually have the standard breakfast, lunch, dinner, plus a couple of small snacks through the day - midmorning and midafternoon, as I have breakfast at stupid-o' clock in the morning and dinner quite late at night...these eating times are non-negotiable, unfortunately.

Currently having cereal and milk for breakfast, a yoghurt and a graze punnet at midmorning, a sandwich or similar at lunch, fruit or toast midafternoon, and a fairly substantial dinner (which I can gradually cut down on portion size for, and can use the leftovers for lunches). What sort of calorie allowance should I be aiming for with each meal? I'm a total gannet, as well, my portion sizes are all out of whack, so I could use some advice on cutting down without feeling so hungry I can hardly think...

I am exercising three times each week, for 45-60 minutes each time. I run, swim, and use the cardio/weights equipment at the gym. At times exercise is hard, as I have chronic urticaria, so I come up in enormous welts in response to various things. Unfortunately weight-bearing exercise is one of them so when I run I get welts on the soles of my feet, when I use the rowing machine I get them on my hands, when I get really sweaty I get them all over. But I am managing at least some exercise, which is better than none, right?!

Anyway, if you made it through that epic post (sorry!) and feel we have things in common, and/or can offer any advice, I'd love to hear from you!