can I use a choke 150uH inductor for my AM transmitter circuit?
Yes, you can use 150 uH inductors if you adjust the values of the parallel capacitors to keep the resonant frequency where you want it.

Yes, you can add fixed capacitors in parallel with your variable capacitors to "center up" the adjustment range around your desired output frequency.  Of course, the adjustment range will be much smaller (more narrow).  You can use the calculator on the website you linked to determine how much external capacitance to add.  The calculator uses total capacitance, so you should subtract 1/2 the max value of the variable capacitor to see how much external capacitance to add.  This will optimize the adjustment range.