I can't seem to do fast-effects after damage is on stack?

I have been having a rough go of trying to do fast-effects after damage goes on the stack. Shouldn't this still be possible?
Two examples:
I have Gore Vassal out. Computer attacks with a 2/2 and 1/1 creature. Shouldn't I be able to block the 2/2 with Gore Vassal, wait for damage to go on the stack, then sac Gore Vassal to kill the 1/1 creature? (understanding that it still does it's damage to me).
Also, computer attacks with a 6/3 enchanted with my Agoraphobia, I block with a 3/3 shouldn't I be able to wait until damage goes on the stack, then return Agoraphobia to my hand and that should prevent the computers 6/3(1/3) from destroying my creature?
It seems once I declare my blockers I have one shot to do fast effects then when I continue past the DB step it seems to just cycle through all the damage phases instantly and everything resolves and then it becomes end of combat. I have even had to use my regeneration at the declare blockers step as I don't seem to have a chance to use it during the damage steps.
Am I doing something wrong or are damage phases not an exact science in Forge yet?
Thanks!
Two examples:
I have Gore Vassal out. Computer attacks with a 2/2 and 1/1 creature. Shouldn't I be able to block the 2/2 with Gore Vassal, wait for damage to go on the stack, then sac Gore Vassal to kill the 1/1 creature? (understanding that it still does it's damage to me).
Also, computer attacks with a 6/3 enchanted with my Agoraphobia, I block with a 3/3 shouldn't I be able to wait until damage goes on the stack, then return Agoraphobia to my hand and that should prevent the computers 6/3(1/3) from destroying my creature?
It seems once I declare my blockers I have one shot to do fast effects then when I continue past the DB step it seems to just cycle through all the damage phases instantly and everything resolves and then it becomes end of combat. I have even had to use my regeneration at the declare blockers step as I don't seem to have a chance to use it during the damage steps.
Am I doing something wrong or are damage phases not an exact science in Forge yet?
Thanks!