Nearly there.....
12V @ 0A7 is ONLY 8W4 I/P so should give 6-7W with reasonable efficiency.
To Measure power correctly use (Peak to Peak X 0.35)Squared/50. So (40x0.35)sqr/50=4W.
You want around 70V (12W) with 13V8.
I'd keep tweaking.
The IRF wont work with ONLY 8V on the gate but the IRL will.
Tune past the best looking waveform till the baseline starts to rise, you'll get way more power whilst sacrificing some efficiency.
Just squeeze and stretch the turns on the O/P toroid to get max power. Leave off the LPF while you do this, can be attached later and it shouldn't change the O/P much...
Str.
p.s. Check my schematic in the ; 'A newbie question about a transmitter' post
sub a 1nF cap for the 1n5 and remove the LPF. So the RF goes thru the 0u1, 7T L, across 1nF to load, simple as..