How much money do you have? How serious are you?
There are any number of tools for part of what you are trying to do, some of which are free AND good. If you need professional logic simulation tools, download either Xilinx or Altera web design tools. They come with schematic libraries for pretty much all TTL parts and are "relatively" easy to get into. You can design a complete FPGA project with these free tools and once you know FPGAs, you might not want to go back to soldering discrete logic ICs, anyway. And given the cost of $10 for an FPGA which will easily let you design the world's most outrageous LED clock, in terms of economics you can't beat programmable logic. Not to mention the fact that "FPGA design experience and VHDL/Verilog skills" on your resume might land you a really great engineering job while "LED clocks from TTL chips" won't do it any longer in a world where the street kids of Bangalore are learning to design VLSI.
But seriously... FPGAs are a lot of fun!
The mentioned SPICE simulators can only do very limited digital and mixed mode simulation. They are great for analog circuits, though, but that does not seem to be what you are doing?
I can't give you any good leads to board layout software. EVERYTHING that is out there for free is essentially crap. And I mean everything. It is a sad state of the open source world that they have not been able to make a single useful schematic/layout tool.
If you can spare about a million dimes ($10k-$100k), you can buy the real mixed-signal tools and professional circuit layout software, although that will be overkill for you. Mentor and Cadence are the companies to go to. But bring money or they won't even talk to you.
Sadly in EDA the old saying that you get what you pay for is almost true.