We've been there too with my lil man Jess, he did block twice last year (in the space of a week)
The good thing is though is if your boy is passing blood and urine then his not blocking.
Jess was on a urinary wet food diet for 8 months before going back onto Felix - which we add water too. Jess isn't a drinker and never has been. He has urinary biscuits still though.
Jess is on 2 cysteases a day - cheaper version of cystaid but with the same amount of glucosamine in, which is what helps them pass the urine. And a Zylkene for stress.
Jess never had any crystals it was all down to stress, we've changed the litter we use and initally gave him different trays to try and we saw a behavourist.
Its only been recently that I've relaxed about checking the trays. I know now Jess well enough to read his signs when his not happy about going to tray (i've been known to go with him and dig about for him)
Its a stressful time all round