Your desires are not compatible.
The entire point of using the contract system in the first place is to add additional challenge to your game, and to structure your space program.
Since you appear to have a very clear idea of what you want to do, and don't appreciate the additional constraints and challenges that come with the contract system, the best thing to do is to not use it.
If you absolutely want to use the contract system, the trick to earning oodles of money is to launch missions that cost far less than they bring in, and using the time between mission events to launch additional missions.
For instance, in the time it takes you to do a Minmus round trip, you can fire off a dozen missions to the Mün, and in so doing make available further Minmus contracts, meaning that the initial cheap mission is made even more profitable by later developments.
Side note: A TWR greater than 5 is almost always a massive waste of money: Unless you absolutely, positively need to get into space immediately you're going to burn most of your fuel fighting needlessly against the atmosphere, and even more in way too steep an ascent.