What you have to find is a compromise - even more than you have already. Both want your attention and both have to give a little. Don't just try to schedule quality time but give them quality time and make sure your boundaries are firm with both. They both want different things really. Schedule intimate times with your partner and activities with your friend. Spend time making each person feel special. If they love you they will adjust. Right now they are in a power struggle but you have to stop participating. When you have time with your friend schedule something fun that doesn't include your partner. Schedule a candlelight dinner that doesn't include your friend. Tell them that you are trying your best to not neglect either relationship. If it comes out that one or the other threaten to leave they weren't your friend/partner to begin with. You have to have boundaries when they don't. When they can engage in a power struggle they will. Both have to adapt.
If this has been helpful press accept
Your caregiving role is interfering with just being yourself. You can't please two people that want you to be two different people. It isn't possible. You have to try to be what you are and less of what they want. If they guilt trip you then you are letting them do so. You have to enjoy their company without adjusting your personality. If they can't get along together then you are going to be faced with finding time for each. So it is in their best interest. You can get them together once and tell them everything including the pressure you feel you are under. If they care about you then they will find a solution. Engage them in the process instead of resolving it on your own. They will be motivated by spending time with you. Turn over the responsibility to them .