You've stumbled over one working solution and had another suggested, but to go into a little more detail:Quote from Mackkie
ok for some reason my crucible furnace is topping out at 1500 degrees no matter what I do I cant get it any higher to melt the rutile ore
ok got it heating up correctly with solid fuel but not with lava for some odd reason
When you have the crucible furnace GUI open, mouse over the fuels you want to use. The tooltip will show you how much any given unit of fuel (1 item, 1 bucket of liquid fuel) will heat the furnace, at most, and also will have a line showing the maximum temperature that can be reached with that fuel. Lava is easily available in bulk (especially if you pump the Nether) but is capped at 1500. Wood has a significantly lower max temperature - you probably wouldn't use it for ores, but it could be handy if all you want to do is melt some fish down. Coal goes up to a full 2000, which is as high as it goes.
You can, for instance, pump into the tank under the furnace for general use, and stoke it up with coal when you need to work with rutile/titanium. It'll build up in temperature; then you can do what you need, remove the remaining coal, and run on the easy fuel.
Edit to avoid double-posting: Would it be feasible to make the fish feeder smarter about consuming fish meal? As it stands, it seems that as soon as the tank is anything other than completely full, it'll gulp down a piece of fish meal to top off. So if it's got room for 1 more mB of food, it'll use up the entire fish meal, fill the tank, and discard the other 11 mB. I'd rather see it either NOT use the item until there's enough room to store the whole item's worth, or have a hidden buffer that can hold whatever the highest possible single-item contribution is if one tosses a raw fish at the thing (maybe with a bit of extra room). That would actually make it pointful to keep fish meal in the input slot, where right now it's incredibly wasteful to do so.