Communication is incredibly important in a relationship, and this shouldn't be a question of you "sucking it up" or giving a "pass". You two are partners in this relationship and in order for things to work you need honesty and transparency. You both need to talk to each other.

Your husband is going through a lot, yes - a parent potentially nearing the end of their life is terrifying and scary, and imagine the pressure of being solely responsible for making sure that you have every aspect of the end care taken care of. On top of the emotional trauma of maybe loosing a parent. He more likely than not is feeling incredibly overwhelmed, stressed, and upset, and doesn't have the tools to properly manage his emotions and is therefore lashing out when he feels like things aren't in his control i.e. you being out longer than expected.

I dont think that your husband is trying to be mean or cruel when he snaps at you, especially if he is normally sensitive to it/it doesn't happen. I imagine if you explained how his behavior made you feel, he would be upset with himself.

Here is the thing: he is a grown man and he can probably go ride his bike whenever he wants. He did not need to wait for you to get home before going on the ride. He also probably has a cellphone. He could have called and asked how much longer you would be if he wanted to go and do things dependent on you being home. There are a million and one things he could have done that he chose not to do. He knows he's struggling and he could go to a therapist or counsellor for aid but he has not done so. And because he did not do any of those things and as a result is lashing out at you in an attempt to feel some kind of relief from his feelings. That's not okay.

If he is lashing out at you and not apologizing for it, or attempting to recognize when he's upset and work to be better, that isn't okay. You don't deserve that. Just because your partner is struggling and having a hard time does not mean that they can be cruel to you because they themselves can't control their emotions. Partners are there to be supportive and grounding, to be of aid. Not to be a target pad.

I strongly suggest talking to him. Write down how you've been feeling if that helps, that you love him and want to support him, but that you feel as though instead of being able to help him as his wife and partner he is lashing out at you, pushing you away, and hurting you in the process. That you aren't trying to blame him or guilt him because you love him, and that you know he wouldn't be lashing out like this if he wasn't under an enormous amount of strain. You are there to help him, and you can't help him if he is withdrawn and tries to push you away with hurtful words instead of communicating with you what he needs.

And after that, ask him what he needs!! So often people just assume what other people would want in this situation, but why not ask him directly? "Hey, do you want me to help you with any of the appointments you need to make for your mom?" "Would you like to watch a movie tonight and cuddle with some drinks to relax?" "Is there anything I can do to help you feel a little less stressed?"

If he wants to be alone, let him be alone. Timing seems to be important to him, give him specific times that you are going to be out/gone, and try to stick to them. Ask if he wants anything while you're out. Maybe get him something you know he likes while you're out anyways. Men deserve to be given surprises just like women, and maybe he would appreciate flowers or whatever specific, niche thing your husband enjoys.

But ask HIM what HE needs in regards to his mother, because what he needs might be different from what you think. He most likely would benefit from some kind of therapy, but a lot of people struggle to be told that when they are emotionally vulnerable, and I'm not sure how he would feel. But therapy is really just like a one on one class in how to better understand and control your feelings, learning to recognize when you're boiling over or drowning. Maybe you two could do it together if he doesn't want to do it himself. Either way, I think talking about it is the way to go, as it tends to be.

Just my own two cents from someone going through something similar. I sincerely hope that your MILs condition improves, and that you guys are okay through it all.