1. Does the device in link #2 above pull an abrasive solution from a container while the nozzle is operating at full pressure, or is a soap nozzle required?
It is made to pull from the container just like a sand blaster using the water flow for the suction instead of air like a sand blaster.
Now, it is hard to say how well it will pull if the solution is too high in solids concentration.
That part would have to involve some trial and error to get the correct consistency as most pressure washers are used for liquid mediums and not much testing has been done in that area to my knowledge.
2. What other abrasive materials can be used in this type of system?
They are normally used for liquids, any solids content will need some further testing.
Just no information on the market using in the way you wish to do, but my thoughts are, it should work well up to probably 20% or so.
May tend to wear out the nozzles, so may need spares handy
3. Can you recommend a different and better alternative?
Just a sand blaster
Have you tried the glass beads in a sand blaster?
Sand tends to have problems with humidity much more than the beads.
Or, peanut shells possibly.
There are many different blasting medias on the market today.
CLICK HERE to see some on the market today
4. Will using 150 degree water improve the cleaning rate?
The higher temperature would certainly help with the cleaning process.
The only thing to look at when using a higher temp, is watching the pump for any problems.
Don't know if thee is any issues with your unit or not, the manual would state if temperature is a problem, but I would say it is not an issue at 150 degrees or so.
Stay aways from anything higher as it could create some flashing at the nozzle.