Speaking from experience, it's much harder to try and communicate with brokers (or indeed any organisation) through web interfaces than through provided API's.
So for example to scrape the positions from IB activity reports is much more involved than making a single API call. Also it's not a supported method. If a broker makes a slight change to their web interface you are screwed. I speak from bitter experience of writing data scrapers - days writing ugly code that worked for about a month before a website upgrade killed it. If they make a slight change to their API they will ensure it's kept backwardly compatible.
Trying to submit orders via the webtrader will be even harder. Quite apart from the fact that IB don't want you to do this, they want you to use the API, and will make it very very hard to do it any other way.
If you change brokers, it will be a lot quicker to write new API code (assuming it's properly isolated) than to write new web scrapers and order submitters.
Seriously, this is insane.
GAT
My friend already use web scraping of well-known yahoo/finance webpage, to feed current prices of 200 watchlist. (although yahoo's data is NOT realtime)
Since it is done already, hope the crucial 5 data in the original OP can be downloaded.
PLEASE note that I have to trade many broker in many country, unlike most traders here involved in SINGLE IB.
If a broker cannot give me easy/satisfactory guide, then I run away, to possibly several alternative brokers.
At least I am NOT addicted and never ever even in other brokers than IB, as well as IB.